Peltier cooling for LNA with Discovery Dish

[Stephen Arbogast]

Has  any one  tried this...   https://www.adafruit.com/product/1335?gad_source=1&gad_campaignid=21079227318&gclid=Cj0KCQjw3OjGBhDYARIsADd-uX47muzSk0Z8lQMMMhtRqA4FAgQRgDH0GXwJcdfZqsxEERrTmvInmK0aAox0EALw_wcB

Thoughts?

[Alex P]

The nooelec SAWbird H1 LNA has a thermal gain coefficient of only  -0.1 dB  per + 10 dgC change

There are typically other variations which greatly exceed this.

[Stephen Arbogast]

Thanks  Alex,

So  I checked  with  Kracken RF    and  my  Discovery Dish  uses this  IC  https://www.mouser.com/new/qorvo/qorvo-qpl9547-lna/

I   don't have  professional  expensive gear to make measurements     just a  Nano VNA  and a  tinySA...

I have  discovered that   the  SOAPY SDR     for AirSpy   in  GNU Radio has  problems     will  need  further    exploration.

[b alex pettit jr]

Just need a nanoVNA, some planning,  & a week of meticulous testing  See Attached

Alex

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

[Marko Cebokli]

Usually, cooling is not for higher gain, but for lower noise. Considering gain, you just want to stabilize the temperature, at whatever reasonable value, like 30C.  Cooling will reduce noise, but in an amateur setup, water condensation and frost are a quite unsurmountable problem. Also, if the antenna is at room temperature, the thermal conductivity of the cable between the antenna and the LNA will be a problem - low electrical loss and low thermal conductivity usually don't dance together.

Marko Cebokli 

2025-09-30 05:50, je 'b alex pettit jr' via Society of Amateur Radio Astronomers napisal

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[Andrew Thornett]

How do you set up cooling? Do you just cool the LNA or do you cool the waveguide too? So for example i use a cantenna for my waveguide - if I wanted to Peltier cool my system, would that mean that I need to somehow cover the entire cantenna and LNA and cool the lot or is just enclosing the LNA in a casing a cooling that sufficient? Then what temperature is ideal? When i am doing astrophotography, I use an Atik 16200M camera which cools to 45 degrees below ambient. I live in UK woth temperature usually in range 15-20 C but can vary 0 C to 30 C. So I cool to -10C which means I can get that temperature at almost any time and the stable single temperature allows me to use a single set of dark frames and flat frames. Does radio astronomy work the same way? Can we calibrate with a single calibration standard used all the time as long as we cool our LNA (or LNA plus waveguide depending on answer to my question above) to the same temperature each time?

Sorry for all the questions but this thread fascinates me as I would love to know how similar radio astronomy and astrophotography are in this regard.

Andy

Sent from Outlook for Android

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Marko Cebokli <s57...@hamradio.si>
Sent: Tuesday, September 30, 2025 1:31:54 PM
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Re: Peltier cooling for LNA with Discovery Dish

 

To view this discussion visit https://groups.google.com/d/msgid/sara-list/a19843243c51d800331589e2c69c4022%40hamradio.si.

[Marcus D. Leech]

On 2025-09-30 09:59, 'Andrew Thornett' via Society of Amateur Radio Astronomers wrote:

How do you set up cooling? Do you just cool the LNA or do you cool the waveguide too? So for example i use a cantenna for my waveguide - if I wanted to Peltier cool my system, would that mean that I need to somehow cover the entire cantenna and LNA and cool the lot or is just enclosing the LNA in a casing a cooling that sufficient? Then what temperature is ideal? When i am doing astrophotography, I use an Atik 16200M camera which cools to 45 degrees below ambient. I live in UK woth temperature usually in range 15-20 C but can vary 0 C to 30 C. So I cool to -10C which means I can get that temperature at almost any time and the stable single temperature allows me to use a single set of dark frames and flat frames. Does radio astronomy work the same way? Can we calibrate with a single calibration standard used all the time as long as we cool our LNA (or LNA plus waveguide depending on answer to my question above) to the same temperature each time?

Sorry for all the questions but this thread fascinates me as I would love to know how similar radio astronomy and astrophotography are in this regard.

Andy

You generally need to cool just the LNA -- the problem is that the LNA usually is in a "thermal marriage" with other components, like the feed-horn.

To get appreciable reduction in noise in an LNA, you have to cool it a LOT.    The professionals cool with LN2 or liquid Helium.    Cooling it down to -10C isn't likely to improve
  noise figure very much, but WILL create condensation/frost management headaches.

The main advantage in any kind of active LNA thermal management is gain stabilization.   You can achieve that in the OTHER direction, using heaters with a PID controller.
  There will be a very small noise figure penalty.    Even doing something like bolting the LNA to a bloody great chunk of steel will help smooth out temperature variations.
  What you'd like is for the gain to be stable-enough over your observing period to get a good total-power measurement of the object of interest.

To view this discussion visit https://groups.google.com/d/msgid/sara-list/FRWP194MB275282815CCB6E87ED6BEE5EFF1AA%40FRWP194MB2752.EURP194.PROD.OUTLOOK.COM.

[b alex pettit jr]

Microwaves101 | Noise Temperature

Microwaves101 | Noise Temperature Microwaves101 | Noise Temperature

#1 : Optimize the Feed vs Dish position and reduce 290K spillover before considering cooling the LNA

Optical Equivalent to focusing the image and not trying to use an open frame Dob in the middle of a bright parking lot

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

[Andrew Thornett]

Yes, not surprised you say those things, Alex, and im sure you are right. I personally wasn't intending to try cooling my setup - however for my interest and intellectual development what are the answers to my questions?

Andy

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From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Tuesday, September 30, 2025 3:16:11 PM
To: 'Andrew Thornett' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Subject: Re: [SARA] Re: Peltier cooling for LNA with Discovery Dish

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[b alex pettit jr]

Ref  Marcus' comments for the answer

[Don Latham]

combine with:

eBay item number:335280036615

controller

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From: "sara" <sara...@googlegroups.com>
To: "sara" <sara...@googlegroups.com>
Sent: Monday, September 29, 2025 5:03:12 PM
Subject: [SARA] Peltier cooling for LNA   with  Discovery Dish

Has  any one  tried this...   https://www.adafruit.com/product/1335?gad_source=1&gad_campaignid=21079227318&gclid=Cj0KCQjw3OjGBhDYARIsADd-uX47muzSk0Z8lQMMMhtRqA4FAgQRgDH0GXwJcdfZqsxEERrTmvInmK0aAox0EALw_wcB

Thoughts?

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

[Stephen Arbogast]

Well...       I have decided  to   not  purchase /try  the  Peltier  Cooler   from  Ada Fruit.   I   am using  a  Discovery Dish   with   Hydrogen   Line  feed.   Velcro   strapping  the   large  chunk of  metal   to  the plastic  case...   enclosing   the  dipole  would  block E&M  waves   and probably not help much  at  stabilizing temperature.. not  to mention  problems  with the  weather. 

I  still  have my  old WiFi dish...   so maybe I  will  set it up again  and try to rig  it with  lna  temp   stabilization..... which  is  weather protected.....

[Stephen Arbogast]

 I  also  use a  TinySA.. it has  a mode  where  it   can  be used as a signal  generator.....  I  find it  useful  for testing..........      https://www.tinysa.org/wiki/

[b alex pettit jr]

IF you ever want to remote the SDR , It has a More significant thermal issue, as do Environmental changes,  than the small -0.1 dB / 10 dgC of the LNA

FYI, you can't use switching power adjacent to the Feed ...

Prof P

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

On Wednesday, October 1, 2025 at 10:26:03 PM UTC-6 Stephen Arbogast wrote:

Well...       I have decided  to   not  purchase /try  the  Peltier  Cooler   from  Ada Fruit.   I   am using  a  Discovery Dish   with   Hydrogen   Line  feed.   Velcro   strapping  the   large  chunk of  metal   to  the plastic  case...   enclosing   the  dipole  would  block E&M  waves   and probably not help much  at  stabilizing temperature.. not  to mention  problems  with the  weather. 

I  still  have my  old WiFi dish...   so maybe I  will  set it up again  and try to rig  it with  lna  temp   stabilization..... which  is  weather protected.....

.

[Stephen Arbogast]

So  I have   the  phase  lock   working  on my   Airspy   R2.....  GPSDO   with  gnu   radio   software not  that  I have two   antennas  but  hoping to try   it..

[Stephen Arbogast]

I   am operating  my    sdr's  in side  my  house..  at constant temp  no problems.   I was curious     about  my lna's   outside  at the  feed point of my dishes..   I have   found  that my   Discovery   Dish  lna    gain  goes  down   with  increasing  temp   as  most  do.     I  am  not   trying  to measure  with   precision.....

[Andrew Thornett]

Hi Stephen

Would you like to have Teams or Zoom meeting about GNU Radio? I am keen to learn more about what you have achieved.

If so, then send me email.at andrew (at) thornett (dot) net and we can arrange a time.

If anyone else wants to take part too then please let me know as well and I'll include you.

Andy

Sent from Outlook for Android

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From: 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Thursday, October 2, 2025 8:14:35 AM
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] Peltier cooling for LNA with Discovery Dish

 

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