more Kraken H1

[Alex P]

6 hour drift scan slices

pk ampl

Dec+20 RA0615 1.5 dB above Cold_Sky

Dec+40 RA2030 1.4 dB above Cold_Sky

Alex Pettit

[andrew....@googlemail.com]

These Kraken feeds (Discovery Dish H-Line feeds) are very good, aren’t they! Cost £120 but do not require a SAWBird as the LNA is built into the device.

I have also found the same with the one I have (purchased after Alex’s recommendation on this group).

Andy

 

 

From: 'Alex P' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: 18 August 2026 12:35
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: [SARA] more Kraken H1

 

 

6 hour drift scan slices

 

pk ampl

Dec+20 RA0615 1.5 dB above Cold_Sky

Dec+40 RA2030 1.4 dB above Cold_Sky

 

Alex Pettit

 

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[andrew....@googlemail.com]

N.B., they work well with other dishes too – I use 140cm communications dish with mine.

Steve presented some excellent interferometry work using 2 x Discovery feed and dishes only 1m apart from each other on Sunday at Drakes – worth watching the video!

Andy

[Conrad Cardano]

Hi

It sounds like the Kraken H1 is better than the "pie pan" antenna...

I'm trying to decide if I should buy the Kraken H1 or build the "pie pan" antenna.

Conrad

To view this discussion visit https://groups.google.com/d/msgid/sara-list/000a01dd2f0f%248bc98e40%24a35caac0%24%40googlemail.com.

[b alex pettit jr]

As they are again ( for a limited time ) In Stock, I'd say get the Kraken .

It includes an LNA /Filter and 20' or so of Coax.

FYI for repeatability, these are drift scans of the same Dec40 region but taken 8 months apart.

The freq changes correspond to the Doppler shift of the seasonal Earth's orbital velocity vector 

from it being on one side vs the other side of the Sun from Dec to Aug

Alex Pettit

======================

[andrew....@googlemail.com]

Hi Alex,

 

Are you saying here that feeds made 6 months apart perform almost exactly the same as each other which is remarkable?

 

Andy

 

 

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: 18 August 2026 14:26
To: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] more Kraken H1

 

ALSO,

These data sets were obtained from Two Different Kraken H1 Feeds .. purchased 8 months apart

 

 

Alex Pettit

=====================

 

 

 

 

 

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[b alex pettit jr]

Also, these data sets were acquired by Two Different Kraken Feeds, purchased 8 months apart

[andrew....@googlemail.com]

Hi Conrad,

 

This is a question I am also keen to get an answer to.

 

Other folks on this group have commented that a pie pan or even a cantenna should out-perform the simple dipole and reflector on the Discovery feed (which is what I think Alex means by Kraken feed – but please can someone correct me if wrong or confirm if right) = so why does it perform so well? Is it about optimisation? And if so in what way?

 

There is something to learn here! (And I would like to learn it!!) [but I need a simple explanation as a non engineer]

 

Andy

 

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Conrad Cardano
Sent: 18 August 2026 13:51
To: sara...@googlegroups.com
Subject: Re: [SARA] more Kraken H1

 

Hi

To view this discussion visit https://groups.google.com/d/msgid/sara-list/CAGewSRvkeqxK84HairrqRjUV9D64awt-k5BqWs0AWH%3DeGKqmgw%40mail.gmail.com.

[b alex pettit jr]

Yes, as they should be if manufactured properly.

( And if the data is acquired and processed by consistent Software )

         ============================================

[andrew....@googlemail.com]

Good – but so much cheap stuff isn’t like that.

 

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: 18 August 2026 14:32
To: andrew.thornett via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] more Kraken H1

 

Yes, as they should be if manufactured properly.

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[b alex pettit jr]

If you recall, the Circular Patch Feed Disk Yagi  has quite similar performance,

 is highly portable and low cost, but takes some careful craftsmanship.

[andrew....@googlemail.com]

Ok thanks

 

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: 18 August 2026 14:46
To: andrew.thornett via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] more Kraken H1

 

If you recall, the Circular Patch Feed Disk Yagi  has quite similar performance,

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[b alex pettit jr]

One last comparison

[andrew....@googlemail.com]

Oh gosh! Just shows how bad that Nooelec H1 feed is!

Andy

 

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: 18 August 2026 15:23
To: andrew.thornett via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] more Kraken H1

 

One last comparison

 

 

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[fasleitung3]

I would be careful with that interpretation. It looks like a big difference, but:

What really counts is the signal to noise ratio. So I would look at the signal compared to the rms noise of the baseline.

Also, the logatimic scale is misleading and exaggertes the actual difference.

Here comes my usual rant: Don't use logarithmic scales in radio astonomy. There is no such thing as dB Kelvin or dB Jansky ;-)

Best regards,

Wolfgang

[b alex pettit jr]

Regards,

Alex

[fdi...@gmail.com]

Dear Alex,

could you please publish the link with the project details and measures of this 18 elements antenna?

I have found the student and the square version, but not this one.

 

Best regards

 

Francesco Di Giovanni, IN3XZP

 

Da: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Inviato: martedì 18 agosto 2026 15:46
A: andrew.thornett via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Oggetto: Re: [SARA] more Kraken H1

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[b alex pettit jr]

Hello Francesco,

Fabrication details . This is the Latest Revision.

https://github.com/AP-HLine-3D/HLine3D/blob/main/21cm_Step1_Antenna_YagiSE_EnhancedRel_Fab04.pdf

Testing

https://github.com/AP-HLine-3D/HLine3D/blob/main/21cm_Step1_Antenna_YagiSE_EnhancedRel_Tests01.pdf

Regards,

Alex Pettit

[Adrian]

Hi,  

  Unfortunately without actual official published circuit diagrams it's difficult to know for certain but it does not appear that a simple dipole on either the Kraken discovery feed or even the feed on the scope in a box dish is what is used. Technically it is called a multi element folded dipole and it has no reflector. it is related to the diagram configuration B which shows a 3 element folded dipole as a representative form of the actual 5 element folded dipole feeds on these dishes. This comparison is with both the SIAB feed and the Discovery Feed indicated inside the blue circle for the Kraken close up image.

The most important clue to this arrangement is the matching network inside the red circle for the Discovery feed.  

  You can see from the impedances listed at the bottom of diagram B that the folded‑dipole configurations sit at several hundred ohms, while the SDR or LNA inputs are a nominal 50 Ω. The very thin microstrip trace coming from the antenna reflects this high impedance, since microstrip width is inversely related to the characteristic impedance of the trace. Where that thin trace transitions into a much wider one, you’re looking at the transmission‑line matching network that steps the several‑hundred‑ohm feed impedance down to 50 Ω before entering the LNA under the shield. In other words, the antenna’s native impedance is nowhere near 50 Ω, so the PCB uses a microstrip transformer to make the system compatible.  

 In any case the antenna obviously is nowhere close to a dipole impedance of near 50 ohms natively. 

 So why utilize this type of antenna feed, because a multi‑element folded‑dipole bent feed gives you a broadband, high‑impedance radiator with a clean, wide beam that illuminates a parabolic dish far more efficiently than any 50‑ohm dipole ever could. 

The high native impedance shapes the current distribution for better gain and pattern stability, the bow‑tie/bent geometry also helps in forming the beam to reduce spillover and improve edge illumination and in addition the multi‑element folding smooths the impedance across a wide band. The thin‑to‑wide microstrip section then is simply the transformer that steps those several‑hundred‑ohm feed impedances down to 50 Ω for the LNA.

 So this type of feed is used because it is broadband, efficient, mechanically robust, and produces the correct illumination pattern for dishes even though its native impedance is nowhere near 50 Ω. 

  Finally the very useful information that is also silkscreened on the PC board within the maroon circle, "PTFE" also indicates that the board design is implemented in a Teflon type  dielectric substrate instead of the inferior FR4. This substrate board material is also known by the brand name Rodgers Duroid and is the type of PC board that is used for all quality microwave circuits due to its superior low loss and dielectric constant which is desirable in the frequency range of these circuits.

   Discussions comparing the active devices used in the Kraken LNA to those in the NooElec Sawbird HI and the potential performance advantages of the Kraken NF device values that are suggested by their datasheets—can be found in a search of previous forum posts by Marcus Leech and others who have described the components for each of the two designs.

Adrian

[Don Latham]

Good look. Isn't there a gridded reflector element at the very front?

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

---

From: Adrian <kjan...@gmail.com>

To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Date: Wednesday, 19 August 2026 1:38 PM MDT

To view this discussion visit https://groups.google.com/d/msgid/sara-list/6e40f830-7c07-4631-b811-a5c087060daan%40googlegroups.com.

[Adrian]

Hi Don,

I'm sorry I’m not sure what you mean by “the front.”

 If it is truly a multi‑element folded dipole—the souped‑up cousin version of the old TV 300‑ohm twin‑lead antennas from the analog age—then the bent bowtie‑type side elements shape the beam and no reflector is needed. 

The actual antenna piece appears to be one single contiguous metal part. The central section seems to be covered under a plastic protection so it’s not really visible, possibly it's there to protect the coax connection from the elements.

 It should be the driven section, with the center of it having the two connections: one to the ground or coax shield, the other side, the center coax conductor being the input to the matching transformer section on the board. The ends of this element then fold into the other adjacent bent elements on either sides of it—see the simple diagram labeled B.

 I don’t actually own either of these feeds, so I’m just going by the online pictures, and maybe someone who does could confirm that the connections going to the section under the center (plastic‑looking) cover have one side of the half wave going to the presumed coax braid or outer conductor, and the center coax conductor branches to the other side of that half‑wave element.

Adrian

[Adrian]

I tried looking at the online pictures again and since I couldn't find any other better ones it could be the metal piece is incorporated as a combined reflector depending on the electrical connections to it or not.

Adrian.

[b alex pettit jr]

Both Sides

[Adrian]

Alex many thanks.

Wow — seeing the actual copper patterns on the other side of the board completely changes the picture. This isn’t a simple folded‑dipole board at all; it’s a genuinely sophisticated microwave feed. The asymmetric ground plane, the via‑coupled parasitic structures, and the shaped planar radiator make it clear that this design is operating at a much higher level than I first assumed.

The LNA input broadband “fat” planar radiator is almost certainly doing the real radiating, and the LNA input is almost certainly coupled at a low‑current, high RF potential node. That kind of weak coupling stabilizes the impedance and preserves the wide bandwidth the designer was aiming for. No wonder the matching network on the opposite side looked like something meant for a high‑impedance source — that’s exactly what it is.

And as Don pointed out, the external metal piece isn’t a multi‑element folded dipole at all — it’s a shaped near‑field reflector that completes the beam‑forming illumination environment for the PCB radiator. When you put all of this together, plus whatever careful RF work likely went into the LNA under the shield, it’s easy to understand why people say this is the such a good hydrogen‑line feed that they’ve used on a dish. The whole thing is remarkably compact for how much engineering is packed into it.

Thank you

Adrian

[b alex pettit jr]

Hello Adrian,

Can you explain Why nooelec changes the focal position for each wavelength on the same dish ?

Thanks, Alex

[fdigio1]

Thanks Alex. 

do you think I could use a threaded rod for the entire lenght of the antenna, providing eventually, a sort of insulation for thr directory from director D1 to D16? 

Best regards 

Francesco, IN3XZP 

Inviato dal mio Galaxy

-------- Messaggio originale --------

Da: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Data: 19/08/26 21:35 (GMT+01:00)

A: sara...@googlegroups.com

Oggetto: Re: R: [SARA] more Kraken H1

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[b alex pettit jr]

Yes.  It just gets heavy .

On Thursday, August 20, 2026 at 05:55:05 AM EDT, fdigio1 <fdi...@gmail.com> wrote:

Thanks Alex. 

do you think I could use a threaded rod for the entire lenght of the antenna, providing eventually, a sort of insulation for thr directory from director D1 to D16? 

Best regards 

Francesco, IN3XZP 

Inviato dal mio Galaxy

-------- Messaggio originale --------

Da: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Data: 19/08/26 21:35 (GMT+01:00)

A: sara...@googlegroups.com

Oggetto: Re: R: [SARA] more Kraken H1

Hello Francesco,

Fabrication details . This is the Latest Revision.

https://github.com/AP-HLine-3D/HLine3D/blob/main/21cm_Step1_Antenna_YagiSE_EnhancedRel_Fab04.pdf

[b alex pettit jr]

Fiberglass Tube works also ( and Carbon Fiber if is has a gloss coating & not surface conductive )

On Thursday, August 20, 2026 at 05:55:05 AM EDT, fdigio1 <fdi...@gmail.com> wrote:

[fdigio1]

So it is not mandatory to insultate the elements from the boom.

Francesco 

Inviato dal mio Galaxy

-------- Messaggio originale --------

Da: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Data: 20/08/26 12:09 (GMT+01:00)

A: sara...@googlegroups.com

Oggetto: Re: R: [SARA] more Kraken H1

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[b alex pettit jr]

It is Mandatory to Insulate the Directors from an Electrically Conductive center support rod.

[Adrian]

Hi Alex,

If you look at the reflector geometries used for the different target frequencies, you can see that each one has a different flare angle. The Wi‑Fi version has the most acute angle, giving the strongest focusing, while the others progressively relax that angle. As best as I can tell, they’re using the reflector shape to crudely modify the antenna beam for each application.

For Wi‑Fi, the signal is essentially a fixed point source, and the user knows exactly where to aim. In that case, you want the narrowest beam you can get from the dish, so they tighten the reflector angle and place the dipole closer to the true focal point to maximize gain at that single direction.

The weather‑satellite version is also aimed at a point source, but the pointing uncertainty is higher. By extending the focal placement of the dipole, they slightly defocus the beam, making the aiming less critical and giving a bit more tolerance for satellite position.

Finally, for hydrogen‑line work, the signal is the least anisotropic of all — it’s coming from a broad region of the sky rather than a single point. So they defocus the beam the most, widening the illumination and trading peak gain for smoother, wider coverage. It’s a very crude way of repurposing one basic antenna for multiple markets.

Hopefully this explanation solved the mystery.

And when you compare their dipole and balun to what the Kraken feed uses, it’s almost painful. The Nooelec design is just a loose foil dipole at the end of a coax, while the Kraken uses a fully engineered PCB radiator with controlled coupling and proper matching. Even if Nooelec had simply moved to a PCB‑based dipole with a real matching network, the performance and reproducibility would be far better than that foil‑on‑coax arrangement.

Adrian

[Andrew Thornett]

This is VERY interesting, Adrian!

Thanks very much to both Alex and Adrian for this in-depth analysis and explanation of why the Discovery H-line feed works so well and why the Nooelec H1 feed does not!

Conclusion:

1. Do NOT buy the Nooelec H1 feed.
2. DO buy the Discovery H1 feed.

Would anyone like to buy a Nooelec H1 feed? I have a couple going cheap!....Special discount for next 24 hours only!!!!!

Andy

Sent from Outlook for Android

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Adrian <kjan...@gmail.com>
Sent: Thursday, 20 August 2026 19:24:24
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: R: [SARA] more Kraken H1

 

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[b alex pettit jr]

Save the nooelec square support tube & base for the Discovery replacement ..

[Miguel Ríos Martín]

From the comments I've read, you recommend the DISCOVERY-H-LINE-FEED-01.

I have a few questions:

Is the DISCOVERY-DISH-01 also recommended, or is it preferable to connect the Discovery feeder to the Noolec antenna?

Is it easy to connect the Discovery feeder to the Noolec antenna?

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[b alex pettit jr]

Hi Miguel,

You have the nooelec Dish .. I'd use that.

Remove the nooelec Dipole & cut down the square tube and use it

to hold the Discovery Feed. ( you can use plastic, tape, etc to hold the Discovery tube in the square Nooelec support tube.

IF you pry out the lower square plastic plug from the square tube,  you can remove it from the nooelec cable, 

tap the black dipole holder assembly out the other end of the square tube and preserve the nooelec feed for further tests .. 

The nooelec Dish works  fine & I really don't have room for another Dish  :)

Alex

[andrew....@googlemail.com]

Hi Alex,

 

This post is exactly what I needed to know too, so thanks for posting.

 

Andy

 

 

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: 20 August 2026 22:46
To: sara...@googlegroups.com
Subject: Re: R: [SARA] more Kraken H1

 

Hi Miguel,

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[b alex pettit jr]

The flange pop-rivets will probably block the white Kraken tube.

About 15 seconds of filing each will solve the problem .

[Miguel Ríos Martín]

One more question: can anyone tell me the outer diameter of the Kraken tube's round arm?

I ask because I have a 20mm SHF20 fitting that might allow me to attach the fitting to that arm.

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Miguel Ríos Martín

[b alex pettit jr]

I measured 19.90 mm OD on one, 19.75 mm OD on the other

[Miguel Ríos Martín]

Thanks, then it fits perfectly with the SHF20 part for attaching the arm to the Nooelec platter

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Miguel Ríos Martín

[b alex pettit jr]

The 48mm spacing for the mounting screws matches the dish holes.

The only  problem is the 36.5mm width will interfere with the other set of bolt heads.. may need to grind it down a bit.

[Miguel Ríos Martín]

I tested the SHF20 part and it fits the dish well; the 36.5 mm length doesn't interfere with the heads of other screws. The 48 mm spacing is a bit tighter because the antenna has 50 mm between its holes. But it's such a small gap that the screws fit perfectly.

With a small washer for the feed arm, it can be positioned perfectly. And it also allows for easy adjustment of the focus distance.

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[b alex pettit jr]

Hello Miguel,

Thanks for that idea : I ordered these to test.

One could be installed on either side of the dish for better stability

Amazon

Alex

[Miguel Ríos Martín]

Yes, I built this circular feeder for the parabolic reflector, and besides fitting very well, it works perfectly.

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[Stephen Arbogast]

This is  all very cool  but  just a reminder.......   the  grid  dish from  Nooelec  is too heavy for the Kraken RF  Discovery  Drive  which should start shipping soon.     I  am anxiously  awaiting mine  so  that I can easily point  my Discovery Dish  for  SDRAngel  Hot/Cold  calibration   among  other   explorations.     Yes,  I know the  HPBW of the  Discovery  Dish is  23 deg but  still much  to learn  and  explore  with  the  Discovery Dish  and Drive....... 

Example...  I have  been watching  the Galactic Plane plot  in  SDRAngel  for  the past 24  hours drift   scan and at first  was  puzzled  why the  Galactic Longitude  reversed  at about  186  deg.    This was very hard for my  brain  to  visualize.    So  from  ChatGPT  I  plotted  the trajectory  of my  latest 24 hour  drift scan  from  my  Latitude of  about  37.3 deg  North,  about  -107.5  deg West   and   got  these  results.   See attached  screenshots....   My  brain  is not  good enough  to  visualize  but  Mathematical  transformation makes it  so.  

If I am totally  off   experts  please let me know.

Stephen

[Adrian]

Hi Stephen,

  Not sure what heavy antenna you are referring to, but in the Nooelec  description of the L band kit as sold by Amazon:

  https://www.amazon.com/GOES-Weather-Satellite-Mesh-Antenna/dp/B08NLDTDM7/ref=pb_allspark_dp_sims_pao_desktop_session_based_d_sccl_2_3/137-6908362-2690767?pd_rd_w=Y4alv&content-id=amzn1.sym.bb57ff9c-59bb-4b04-a98f-485dda19cac2&pf_rd_p=bb57ff9c-59bb-4b04-a98f-485dda19cac2&pf_rd_r=3Y8JT1X3FR3X9ZP0208S&pd_rd_wg=iSQ1i&pd_rd_r=d9b16729-c675-4e1f-bab1-43d807e96aec&pd_rd_i=B08NLDTDM7&psc=1

 The description reads ;  - The included antenna is a high-performance L-Band GOES weather satellite parabolic antenna. It has a gain of ~21dBi and an LMR400 cable terminated with male SMA connectors to connect to your gear. The antenna is linearly polarized (vertical or horizontal depending on the mounting), with an electric field aligned with the main reflector and feed-point grid lines. It can be deployed for both linearly and circularly polarized signals (RHCP and LHCP). Assembled antenna dimensions are 0.99m x 0.61m x 0.38m (39" x 24" x 15"). It weighs about 2kg (70.5oz). So it's only 2 kg and the  Kraken RF  Discovery  Drive states ;     Rotator Specifications-Up to 125 kg · cm (12.25 Nm) of torque (suitable for antennas up to 5kg.

So it could carry up to twice the weight of the Nooelec antenna it seems.  Also $800 seem a bit steep for a small rotator like it and although I am sure it is very well built, there are some lower priced units that could be useable. For example look at the ,  The AntRunner Rotator   from Tinde @ 

https://www.tindie.com/products/johnnywu/the-antrunner-rotator/. 

  At  only $325  it seems to have almost the same specs as the Kraken ;

   Specification

● Rotation Limit: AZ: 0 - 360°; EL: 0-180°

● Max Load: 5KG

● Backlash: AZ:1° EL:1°

● Weight: 3.1KG

Here is a good you tube video on the AntRunner also   https://www.youtube.com/watch?v=Rim9VQKrIT8    Funny, they show it being used with the Kraken dish in the video.

It might also work well enough for the casual radio astronomy needs of the average observer.

Adrian

[Don Latham]

Got an antrunner.  It's well made, but has no position measure. So, wherever you are according to the pulses sent to the steppers, that's where you point. It also is not by any means weather proof, I've been trying to come up with simple angle measure schemes; the elevation will be ungainly but simple, whereas the azimuth is still not decided on. Even if that's done, the drive software has to be redesigned for feedback control and hooked to something like pstrotator or Radio Sky. As Roseann roseannadanna has it, it's always something. Antrunner is a good starting point for experimentation..

Don

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

---

From: Adrian <kjan...@gmail.com>
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Date: Saturday, 22 August 2026 3:52 PM MDT

Subject: Re: R: [SARA] more Kraken H1

To view this discussion visit https://groups.google.com/d/msgid/sara-list/4b577e2b-33d5-40d8-8eb1-71c77c82640en%40googlegroups.com.

[A. C.]

Don,

 Thanks for the feedback, I ran across the system on youtube and was looking at it for possibilites. Is there a way to add on some position/rotation sensors for the feedback loop.?

In the video they claim that with use of Satdump and Hamlib they can track and decode sats with it, so I wonder if Stellarium could also be made to work for RA.

Yes my main concern would br the open framework and the need for some waetherproof enclosure if it is to be kept outdoors.

Still for the price, it sems like a good system to hack even if it isn't plug and play.

Adrian

[Ayushman Tripathi]

Hi Alex,

Really nice data. I was just wondering, as you advised me earlier that cantennas are better than these feeds for a large dish because the cantenna’s bandpass filtering by design rejects cell RFI and so on. But have you ever tried this DD feed on a large dish, to compare it directly against a cantenna, so we can see the results side by side?

I wanted to try this myself, but attaching a DD feed on a large dish does not seem easy without custom fabrication.

If this feed is really engineered as well as it looks, I think it is worth trying once.

Thanks,

Ayushman

[Ayushman Tripathi]

Hi Adrian,

Thanks for the explanation with the beam defocus theory, it really makes sense. But what if Nooelec simply didn’t test these much? They may have just used stock parts for each product without much optimization, which would fit with what Alex pointed out, that the feed doesn’t sit at the optimal position in the stock system.

Thanks

[Ayushman Tripathi]

Hi Adrian and Don,

What do you think about this dish rotator? It’s rated IP66 waterproof with a 10 kg max load, and from the images it seems to come with both app control and a remote. I found it last month but I’m unsure how I would mount my smaller dish on it. Have you tried anything like these? I’ve seen it go for around $100 at times, which is much cheaper than the AntRunner.

One catch is the tilt range is only ±45°, so it might need a tilted mounting bracket or a modified home position to get proper sky coverage. 

https://www.alibaba.com/product-detail/2025-New-Design-Ip66-Waterproof-Auto_1601594242004.html?spm=a2700.prosearch.normal_offer.d_title.7e8c67afj2jmJa&priceId=b475edaeacbc4fd6ba4a0cd8269c8663

Thanks

[b alex pettit jr]

Hello Ayushman,

Someday, when the weather is more stable in Fla than it is now,

 I will install the DD on my 1.2m system to compare it against the LF .

Yes, Cantennas have the advantage of having inherent band-pass , but they are bulky and heavy for small systems.

I did test  the Cantenna  against my Loop Feed and found Equal Performance

( the low values were due to a not as yet optimized design of the panel extensions in '22 )

Alex

[Adrian]

Ayushman,

Sure, they could have assembled the kits using whatever materials they had on hand, If the aluminum feed‑support lengths were really random, we would expect to see a mix of focal‑length errors across the product lines. In other words, some HI hydrogen feeds should have shipped with shorter supports that accidentally put the feed closer to the correct focus, and some WiFi feeds should have shipped with longer supports that pushed the feed too far out. But that never seems to have happened.

Instead, each product category consistently shipped with its own specific support length. The HI hydrogen feeds all arrived with the same “too‑long” focal‑length support, and the WiFi feeds all arrived with the shorter in focus supports appropriate for their intended application. That consistency strongly suggests the lengths were deliberately chosen, not random or improvised at assembly time.

So the question becomes: if they were simply grabbing whatever support rods were available, why did the HI hydrogen feeds always end up with the longer, out‑of‑focus supports? The repeatability across all delivered units implies intentional selection rather than chance.

I haven’t seen whether the actual dipoles and baluns for each application are built to the proper dimensions to approximate resonance as well as the simple design allows, but I assume each one is at least attempting to operate in the correct frequency band for its intended use. A WiFi dipole, even if someone tried to tune it for 2.4 GHz, would be completely inadequate for the 1.4 GHz hydrogen line, and likewise for the 1.6 GHz band, and so on.

I don’t know for certain what their design intentions were, but for a company that does have some reputation for supplying this type of equipment — even if the designs are minimal — I think they are at least trying to provide a product that meets the basic criteria for each application. Even at low cost, they seem to be making an effort to match the feed elements to the appropriate frequency band rather than simply reusing one single feed dipole. By modifying the antenna’s beam geometry with a single design, they’re able to reduce cost while trying to optimize its use across their various market applications.

Adrian

[Adrian]

Ayushman, 

The DD Kraken feed PCB figures that Alex shared appears to be of a very broad‑bandwidth radiator design. Without someone actually putting it on a VNA or spectrum test bench, it’s hard to say exactly what bandwidth it covers, but the design cues strongly suggest a wide frequency response, and at minimum it seems well‑matched to the LNA input impedance. It could be that Kraken even uses the same PCB radiator across their entire product line, much like NooElec attempts to do, and that the primary differences between applications come from the LNA and the SAW filter choices for each specific band they support. If that’s the case, the wideband PCB element would serve as a general‑purpose radiator, while the band‑defining selectivity and gain characteristics would be handled almost entirely by the front‑end electronics. One would have to see examples of their other product PCB to get some idea if this is true.

The clues are in the geometry. The broad radiating elements are a hallmark of wideband behavior, whether in a monopole, a PCB trace radiator, or any other planar antenna. Even more telling is the stepped section — the part that looks like a staircase. That feature is directly analogous to the element scaling used in a log‑periodic dipole array (LPDA). Log‑periodic antennas are intentionally designed to cover multiple octaves of frequency, and they use asymmetrically coupled resonant elements to smooth the overall response. The PCB pattern on the Kraken feed shows the same design philosophy: multiple differently sized segments, each contributing resonance over a different part of the band.

Beyond visual inspection, it’s hard to say more about the exact resonant behavior of the PCB elements, but the additional impedance‑transforming section — stepping from a very high feed impedance down to something the LNA can accept — helps make the radiator less sensitive to the wide frequency range it’s intended to cover.

Alex is also correct about the waveguide nature of a cantenna. A cantenna has inherent frequency selectivity because its dominant mode (TE₁₁ or TEM‑like depending on geometry) only propagates efficiently over a narrower band. That natural selectivity can help reject nearby RFI sources such as cellular bands. A well‑designed cantenna feed, properly matched to a specific observing frequency, should perform as well as the Kraken PCB radiator in terms of frequency discrimination.

The efficiency and characteristics of the front end electronics then provide the system differentiations from each other. The Kraken feed has one major advantage: its integrated LNA. The LNA is likely superior to what most people bolt onto a cantenna, and because it’s directly connected to the PCB radiator with no cables, connectors, or transition losses, the overall noise performance is better. The absence of connector interfaces eliminates several tenths of a dB of loss right at the front end, which matters enormously for weak‑signal work.
Finally, the Kraken feed — with its near‑field reflector beam forming function and most likely the actual PCB radiator itself — was almost certainly designed, at least to some degree, for the small Kraken dish they also sell. That dish’s F/D ratio and illumination characteristics are not the same as the wide variety of random dishes people are using in the field. Because of that, the Kraken feed, which is not easy (and in some cases not really possible) to modify or re‑optimize for other dishes, cannot be expected to perform equally well on every other dish it is placed on. Its efficiency and illumination will vary, and in some cases may be noticeably reduced, simply because it was never intended to be used on those geometries.

  Finally, I’m not advocating for the DD feed, but the reason I went into all that detail is simply because its design, bandwidth behavior, and dish‑specific illumination make a direct comparison to a cantenna on a large dish far less straightforward than it might seem.

Adrian  

[andrew....@googlemail.com]

I remember discussing mounts with Rich and others, and as far as I could see there isn’t a good mount that takes radio dishes and easily connects to Stellarium or something similar – or am I wrong?

Andy

 

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of A. C.
Sent: 23 August 2026 03:00
To: sara...@googlegroups.com
Subject: Re: R: [SARA] more Kraken H1

 

Don,

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[ja...@ganssle.com]

Adrian,

 

Not sure if this is useful, and I haven’t written anything up about this as yet, but I’ve built a 1.5 meter dish and want to try to use long integrations. So, I’m building a mount that will track in RA and eventually declination. Here’s a picture of it on my bench:

 

The shaft will go to the dish to track in RA. There are two encoders to give absolute position. On the left is a 600 pulse/rev incremental encoder that is geared down 4 to 1 (black gears on the left). It also has a once/rev index pulse, but because of the gearing the code doesn’t know where the shaft is. The 8-position encoder is a 3D printed disk with 3 slots to encode position; LEDs on one side shine through it to optotransistors on the other side. So, that encoder tells the code about where the shaft is. (It’s not binary coded; it’s Gray code to avoid positioning uncertainty on the edge of slots).

 

The PCB is a custom-design. The 600 ppr encoder interrupts the Arduino on that PCB 4 * 600 times/rev, but it’s set up to interrupt on both edges, so that’s a resolution of 4800 counts/rev.  That’s pretty close to the stepper motor’s resolution as well, due to internal gearing and the 30:1 worm gear.

 

The motor drivers have fans, but a recent software change has made those unneeded.

 

The 600 ppr encoder was $15 on eBay, the stepper $35 on Amazon, and most of the other stuff is 3D printed. There are ball bearings at each side of the shaft. The bare PCB was $20 (for 5 copies, including shipping) from JLCPCB in China.

 

The software all works but I’m planning to build a duplicate of this for declination, and am modifying the code to handle that as well (the one PCB will run both RA and dec).

 

Oh, to aim it I’ve printed a waterproof box for the LNA that goes on the end of the feed. There’s a camera on the box so I can use Sharpcap or NINA to plate solve. Since the encoders working together are absolute, I will be able to plate solve at night on stars, and slew anywhere during the day. The camera will not be powered when doing radio astro to avoid RFI.

 

If one were to buy a mount with encoders for astrophotography the encoders would be accurate to better than an arcsecond; this has a resolution of only about 5 arcminutes, but that’s plenty for radio astro with a small dish.

 

Stellarium does have an API so I suppose this could be connected to it, but I really don’t see a reason to do so. My software takes RA and dec as inputs to slew to.

 

No doubt bugs will surface as I deploy it all. But that’s the fun of engineering!

 

Jack

N3ALO

To view this discussion visit https://groups.google.com/d/msgid/sara-list/000c01dd32fe%24bac68fc0%243053af40%24%40googlemail.com.

[Don Latham]

Not sure about using 2.5 GHz remotes. Might be 

OK if not on all the time and you don't want to track, but set and use earth rotation.

 

---

From: Ayushman Tripathi <ayushmantr...@gmail.com>

To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Date: Sunday, 23 August 2026 2:14 AM MDT

Subject: Re: R: [SARA] more Kraken H1

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[Don Latham]

you are not wrong.

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

---

From: andrew.thornett via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
To: sara-list <sara...@googlegroups.com>
Date: Sunday, 23 August 2026 6:55 AM MDT
Subject: RE: R: [SARA] more Kraken H1

To view this discussion visit https://groups.google.com/d/msgid/sara-list/000c01dd32fe%24bac68fc0%243053af40%24%40googlemail.com.

[Ayushman Tripathi]

Hi Alex,

Thanks. I will also try to build a loop feed for my smaller WiFi grid dish, since with that I can at least put a filter before the LNA. Right now with DD feed in urban RFI, it gets overwhelmed. Building a cantenna would be bulky, as you said, and would need 3 fabricated arm mounts, which is harder than just putting a loop feed on the existing WiFi feed arm I already have.

My 2.4 m dish system is doing well with the cantenna. I wasn't able to build the choke ring for it, but I will try on my next cantenna. I'm thinking of getting a 3D printer to 3D-print cantenna, etc., with copper tape or pasted aluminum foil so I can build more without relying on custom metal fabrication, as I'm scared to buy/handle an angle grinder or any metal cutting equipment.

Thanks,
Ayushman

[Ayushman Tripathi]

Hi Adrian,

That makes sense. Like you said, the consistency across units does suggest the lengths were chosen deliberately, random leftover stock would have given random errors or at least different lengths in different batches, and that never happened.

Also, I never got one of those Nooelec feeds. When I started in RA, I searched the web for radio astronomy with a HackRF (the SDR I had) and found a blog on the RTL-SDR website showing it :) so I directly got the DD feed as my first feed. (attached page)

Thanks.

[b alex pettit jr]

Hi Ayushman,

You can try this but it will be a real performance killer.

 ....   put a filter Before The LNA. 

https://www.microwaves101.com/encyclopedias/noise-figure

Alex

==========================================

On Sunday, August 23, 2026 at 04:51:14 PM EDT, Ayushman Tripathi <ayushmantr...@gmail.com> wrote:

Hi Alex,

Thanks. I will also try to build a loop feed for my smaller WiFi grid dish, since with that I can at least put a filter before the LNA. Right now with DD feed in urban RFI, it gets overwhelmed. Building a cantenna would be bulky, as you said, and would need 3 fabricated arm mounts, which is harder than just putting a loop feed on the existing WiFi feed arm I already have.

[Ayushman Tripathi]

Hi Adrian,

Thanks for the detailed explanation, it really helps. The LPDA-style stepped sections explaining the wideband behavior make sense. I'll try to see if I can find images of the PCB of Kraken's other feeds from other web forums and will post here, and also your integrated LNA with no connector losses point is very good.

Regarding dish-specific illumination points, yes, I wondered about it before too and even reached out to Kraken directly to ask them about that, here was their reply:

The Kraken <thek...@krakenrf.com>
Wed, Dec 3, 2025, 9:34 PM
to me
Hello Ayushman, 
Thanks for the purchase of a Discovery Dish H-Line Feed. 
We designed the feed to work with the Discovery Dish specifically. It's possible that it will work with your 2.5-meter reflector, but we have no idea how well it will work. I can only say that you may want to experiment with it. 

——-EMAIL END——-

Also, this is what they mention about dish compatibility on their GitHub page:

Dish Compatibility: Best with the Discovery Dish, but works with most prime focus dishes using an adapter, including typical 600x900 mm WiFi Grid Dishes.

https://github.com/krakenrf/discoverydish_docs/wiki

Thanks,
Ayushman

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[Ayushman Tripathi]

Hi Alex,

Thanks. Yes, the filter loss before the LNA will hurt the noise figure badly, but I'll try anyway, because currently it's not detecting anything most of the time, all it sees is RFI :) so there's no performance to lose in the first place. When I try this I'll post the results, though like you said, I'm not sure it will be enough to make it work. If it doesn't work, I'll move this dish to the same location as my bigger dish, since that one works nicely there with almost no RFI and no such issues.

Thanks

[Ayushman Tripathi]

Hi Don,

Yes, that's a good point about the 2.4 GHz remote interfering. I will check if it uses an open-source protocol, and then maybe it can be automated using a Pi or similar, sending commands to it with a 2.4 GHz transmitter and using a digital compass module on it (magnetometer for azimuth and accelerometer for elevation, I guess) to feed the Pi its current pointing.

Yes, I mostly don't want to do tracking.

Thanks

[Don Latham]

I just had  a thought about the +_ 45 degrees. Can't the appropriate choice of mounting angle allow coverage of a full 90 degrees of declination? Then you can use ra and declination to set the mount. Gee. and for a very good price, too. to quote a close acquaintance, D'OH.

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

From: Ayushman Tripathi <ayushmantr...@gmail.com>
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Date: Sunday, 23 August 2026 3:58 PM MDT

To view this discussion visit https://groups.google.com/d/msgid/sara-list/dd9b1b95-ffd9-4b9a-a70f-8737da6eaff0n%40googlegroups.com.

[fasleitung3]

I am putting this comment outside the original thread as it has become quite long.

Usually the weight a rotator can carry is not the issue. The main characteristic is the torque it can provide. It is specified for the Kraken Discovery Drive but not for the AntRunner so one cannot really compare the two. Also, one needs to remember that the required torque is not just determined by the dish alone, but also by the wind load on the dish. The torque required to operate the dish even under moderate wind conditions can exceed what is required for the dish alone.

Another consideration is the weather: While the Kraken Discovery Drive is specified for IP55, the AntRunner is completely open. So the two devices are not comparable in that respect.

Best regards,

Wolfgang

[Stephen Arbogast]

Thank  you   Wolfgang,

Here in  South  West   Colorado..   we  get  heavy  winds   that  can occur  unexpectedly.......  mountain conditions........   rain  and  ice   is  brutal here.

Stephen

[Andrew Thornett]

Colorado = Ted Cline has a wonderful photo of a dish that has folded Taco style. Even here in Staffordshire, UK, hardly the location of most extreme weather, I have had entire mounts and dishes blow over causing serious damage to the dish.

With regards to this question of going beyond simple drift mounts (which work really well because they can be made very robustly without difficulty), to me the messages that comes out of this discussion are:

1. The mount needs to be rated for several times the mass of the dish to compensate for torque and wind.
2. The mount needs to be waterproof if left outside 24/7.

I do not know enough to say how many times the mass it needs to be rated for.

Perhaps Wolfgang or Adrian can tell us how to calculate this?

Working on the basis that KrakenRF seems to be engineering their kit to a high level (a la Alex and Adrian's recent analysis of the H-line feed), and guessing that they are matching their bits of kit to each other, it would seem reasonable to suggest that the Discovery dish+Discovery feed+Discovery mount ought to work well.

BUT:

1. No guarantee it won't be damaged in high wind or bad weather.
2. From my reading of the Crowd Supply website, I can't see evidence that the Discovery mount connects to astronomy software to control pointing - does anyone know better?
3. Of course you are limited to 70cm dish and the limited resolution that gives. BUT PERHAPS A MOUNT IN THIS PRICE RANGE (SUB-£1000) CAN ONLY CARRY EFFECTIVELY AND SAFELY A 70CM DISH - I need someone with better knowledge than me to tell us the answer to that question.

All of us would like a fully steerable 1.5-2m dish in our garden, but the real question is - is that reasonable at < £1000 for the mount?

.....Then there is of course a Paramount or a high capacity strainwave/harmonic mount - that should do the job but costs a bit more (but even then weatherproofing might be poor).

Andy

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From: 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Monday, 24 August 2026 08:33:26
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: [SARA] Re: Antenna rotor specification, was more Kraken H1

 

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[Stephen Arbogast]

Dr. Andy,

I have a lot  of respect for you, I am from  a  medical   family...   but you are  not speaking  Physics.

1. Ted  Cline is  not the one and only Colorado..  we  are a very  diverse state  with  various Geographical  features. I live on the Colorado Plateau  in South West  Colorado   which is  very           different  from where Ted  Cline   lives.

2. You speak of mass of the  antenna.... not  important    ...  torque is  important.

3. Software  support is  good....    Stellarium, GPredict, SDRAngel

4. It is  weather proof

5. Even  Alex  who is very   tough  on antennas  has  given the  Kracken  Dish  and HI feed good marks. 

6.  What  the hell is a Paramount or a high capacity strainwave/harmonic mount - that should do the job but costs a bit more (but even then weatherproofing might be poor).

[Andrew Thornett]

I get the feeling Stephen that I have caused offence in some way..my apologies for that.

Andy

Sent from Outlook for Android

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From: 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Sent: Monday, August 24, 2026 10:46:04 am

To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Subject: Re: [SARA] Re: Antenna rotor specification, was more Kraken H1

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[Adrian]

Jack,

 You seem to have designed a very compact and accurate positioner. Do you have also an azimuth one in the works.?

Hopefully you will write your construction up for ideas with others interested in a customized dish pointing design.

Adrian

[ja...@ganssle.com]

Adrian,

 

Yes, another is in the plan for the declination axis. If this all doesn’t turn out to be catastrophically bad I do plan to write it up.

 

Jack

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[Don Latham]

Thanks,  Wolfgang.   Can I suggest for a torque refresher

 https://www.youtube.com/watch?v=TQQXpFhACSU

 

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

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From: 'fasleitung3' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
To: sara-list <sara...@googlegroups.com>
Date: Monday, 24 August 2026 1:10 AM MDT
Subject: [SARA] Antenna rotor specification, was more Kraken H1

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[Ayushman Tripathi]

Hi Don, Yes I’ll consider it, Thanks for help.

On Sunday, August 23, 2026 at 6:49:10 PM UTC-4 Don Latham wrote:

I just had  a thought about the +_ 45 degrees. Can't the appropriate choice of mounting angle allow coverage of a full 90 degrees of declination? Then you can use ra and declination to set the mount. Gee. and for a very good price, too. to quote a close acquaintance, D'OH.

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

From: Ayushman Tripathi <ayushmantr...@gmail.com>