Initial experience with Ukranian transverter and HL2

[Bill Cox AK3Q]

I bought this dual-band UHF/VHF transverter from Ebay.com.  For $145, I can't complain, but it has limitations.

First, it has no remote control, and reports no telemetry.  I'll leave the "freq+" button on, to set the 28MHz on the HL2 to correspond to 146MHz on the antenna.  There is probably about 2MHz of useful bandwidth I can use remotely through the transverter.  The ability to do 70cm is almost useless.  Even if I do physically press the button, this combo only covers about 15% of the 70cm band if I want to stay within about 27MHz to 31MHz on the HL2.

Finally, there are sound quality issues.  I don't yet know the reason for this, so I can't be sure it is the transverter.  On some stations, I hear noise that sounds like popcorn popping.  My little RTL-SDR does not hear this noise.

I'd love to upgrade to a better transverter that is remote controllable, and reports telemetry.

[Mooneer Salem]

Hi Bill,

I have the "high stability" 2m only one and I've not been impressed so far. Mine seems to need a preamp in front of it in order to have anything close to equivalent performance vs. my Kenwood FM mobile rig, let alone better. Plus, I've had ground loop issues when trying to get the required TX sequencer working. It's very possible there's user error somewhere but I haven't had a chance to explore much since I got it. Suggestions would definitely be appreciated.

Thanks,

-Mooneer K6AQ

--
You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/dbd2ac32-1d51-45f3-be56-304d51bc7698n%40googlegroups.com.

[Bill Cox AK3Q]

I have to agree.  The HF performance of the HL2 seems very good.  I don't have a lot to compare it to, but I actually know a bit about audio (lookup libsonic on Linux sometime).  The HL2 may not deliver 16-bit audio, but at least where I live, it takes a booming signal for that to be noticeable.  I hear folks complain that a nearby loud signal will drown out a 12-bit ADC, but I haven't experienced that with the HL2 so far on HF.  On the otherhand, on VHF with my transverter...

73, bill ak3q

[Steve Haynal]

Hi Bill and Group,

libsonic looks very interesting. Is it used in any ham applications?

With the DSP processing from 76.8 MHz down to 48-384 kHz IQ, we see some meaningful processing gains. This adds from 3-5 bits of resolution to the final IQ signal. So given the effective number of bits of the ADC in the HL2 is closer to 10 (even 16-bit ADCs have around 12 effective bits), each IQ channel can have 13 to 15 bits of meaningful data even though 24-bit IQ data is sent back to the computer. After further demodulation in software to 6kHz mono audio, the processing gains are such that there can be 17 to 18 bits or real audio data. I've found this article very useful to understand and reason about SNR in SDR:

https://www.analog.com/media/en/training-seminars/tutorials/MT-001.pdf

73,

Steve

kf7o

[Bill Cox]

Thanks for the link Steve.  That nerd-sniped me, and I spent a few hours trying to grok the Quisk S-meter, the AD9866 LNA signal path, and thermal noise limits, and the limitations of a 12-bit A/D for an SDR receiver.  All fascinating!  I also checked my own antenna vs 50 Ohm dummy load.

The TL;DR: The HL2 seems to have enough resolution given the QRM on my 40m long wire antenna.  Also, IIUC, an "S9" signal should be reported for any signal rising about 27 dB over the FFT noise floor.

My antenna noise appears about 4 dB over noise from my 50 Ohm dummy load, as seen in the Quisk graph.  More resolution would simply increase the difference in the noise I see from my dummy load vs my antenna.  So, until I move out to the country and buy a tower and Yaggi, a more expensive SDR with better resolution won't do me any good.

The S-meter is Quisk took me a while to understand.  Folks should know that Quisk displays voltage, not power, so 3 dB is a factor of 2 in voltage, which is 6 dB in power, which is roughly 1 S-unit.  If you see a signal rising 27 dB on the graph over the FFT noise floor, IIUC, that should be reported as S9.  Does that sound right?

I found with the dummy load that on all bands, the FFT noise floor was about -136 on the main graph, with the LNA set to -12.  With the dummy load, there was no increase in the noise floor as I increased the LNA gain until around -8 dB.  After that, the FFT noise floor increased roughly the same as the LNA increase.  However, with my antenna plugged in, HL2 set to 10M, ATU in the HR50 active, AGC off, and LNA = -12, the noise floor increased to about -132 (higher for higher bands, especially 80m).  It increased linearly with LNA as I increased LNA until Quisk reported clipping at about LNA = 29 dB.  So, IIUC, QRM from my antenna dominates even with LNA = -12, while internally generated noise in the AD9866 dominates from about -12 to -8 dB if the antenna input is grounded through 50 Ohms.  The thermal noise generated by my 50 Ohm load should be about 5uV up to 30MHz.  An A/D with a 2-volt range would need 19 bits to consistently see the LSB toggling.  With the HL2's 8-to-1 transformer in the RX path, a 16-bit A/D could reliably detect the thermal noise.

BTW, my second and third Quisk receivers that I typically display using the "Add Rx" button, had a higher FFT noise floor, by about 3 dB.  I suspect Quisk uses an FFT 2X smaller for all additional receivers displayed.

As for applications of libsonic, I am considering writing a hack to let me listen to two conversations at the same time.  I normally listen to my screen reader at 4X speedup (about 600 wpm).  I prefer listening to humans at around 3X speedup.  Listening at 2X speedup, I should be able to listen to two different conversations at the same time.  I'll buffer both receivers, increase the speech rate by 2X, and merge both streams heuristically, at low-signal points corresponding hopefully to the end of sentences.  I'll lag behind by several seconds, but if I am not expected to respond, that should be no problem.  It could, for example, let listen to a conversation on HF while taking part in a net on our local VHF repeater.  I'm not sure how that will feel in my head, multi-tasking across conversations, but I'm looking forward to finding out.

73, Bill ak3q

You received this message because you are subscribed to a topic in the Google Groups "Hermes-Lite" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/hermes-lite/NnD2_GrKQKw/unsubscribe.
To unsubscribe from this group and all its topics, send an email to hermes-lite...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/76eb75d5-597f-4da2-9543-8be4366b4282n%40googlegroups.com.

[Steve Haynal]

Hi Bill,

Thanks for the update and for building/distributing the HR50 boards. It looks like you ran some interesting experiments. I don't consider myself an expert in this area, but do know that process gains are real after working on the DSP code in the gateware.

73,

Steve

kf7o

[Roger David Powers]

Bill and Mooneer (and others too):

Did anyone find any improvements with the use of these inexpensive transverters since these reports from September, or are they in the junk pile now?

I ask because my interest in being on 2m and 70cm has gone up a lot recently, due to some projects people around me are working on, and I have found at least one feasible way to get a usable antenna in the air.

The eham article linked earlier ( https://www.eham.net/reviews/view-product?id=14939 ) gives suggestions to add heat sinks, add PTT, add a resistor to reduce drive level and to add rubber feet to keep the unit from moving around the desk. 

The conclusion says:

After the mods, you end up with a frequency-stable and cool running transverter with a better sensitivity compared to the FT817nd. Not bad at all.

but this seems to be at odds with the comments below.

I agree with the comments that it'd be nice if there was something better on the market, but given I'm a software guy as opposed to a RF engineer the next step up (and it's a big step) seems to be the q5signal unit for $2000.  I'd be more willing to futz around with something like the "pluto+" boards that have shown up on ebay (pluto clone with ethernet and better clock) and add external preamp/amp as needed.

Regards,
RDP

On Tuesday, September 7, 2021 at 11:25:27 AM UTC-7 moo...@gmail.com wrote:

Hi Bill,

I have the "high stability" 2m only one and I've not been impressed so far. Mine seems to need a preamp in front of it in order to have anything close to equivalent performance vs. my Kenwood FM mobile rig, let alone better. Plus, I've had ground loop issues when trying to get the required TX sequencer working. It's very possible there's user error somewhere but I haven't had a chance to explore much since I got it. Suggestions would definitely be appreciated.

Thanks,

-Mooneer K6AQ

On Tue, Sep 7, 2021, 10:54 AM Bill Cox AK3Q <waywa...@gmail.com> wrote:

I bought this dual-band UHF/VHF transverter from Ebay.com.  For $145, I can't complain, but it has limitations.

First, it has no remote control, and reports no telemetry.  I'll leave the "freq+" button on, to set the 28MHz on the HL2 to correspond to 146MHz on the antenna.  There is probably about 2MHz of useful bandwidth I can use remotely through the transverter.  The ability to do 70cm is almost useless.  Even if I do physically press the button, this combo only covers about 15% of the 70cm band if I want to stay within about 27MHz to 31MHz on the HL2.

Finally, there are sound quality issues.  I don't yet know the reason for this, so I can't be sure it is the transverter.  On some stations, I hear noise that sounds like popcorn popping.  My little RTL-SDR does not hear this noise.

I'd love to upgrade to a better transverter that is remote controllable, and reports telemetry.

--

You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/dbd2ac32-1d51-45f3-be56-304d51bc7698n%40googlegroups.com.

--

You received this message because you are subscribed to a topic in the Google Groups "Hermes-Lite" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/hermes-lite/NnD2_GrKQKw/unsubscribe.
To unsubscribe from this group and all its topics, send an email to hermes-lite...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/76eb75d5-597f-4da2-9543-8be4366b4282n%40googlegroups.com.

--
You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.
To view this discussion on the web visit

https://groups.google.com/d/msgid/hermes-lite/50a291d7-b97f-409e-8f1a-0d83c2e5a042n%40googlegroups.com

.

[Mooneer Salem]

I actually got time to play with my transverter recently. It turns out that at least part of the issue was due to the amplifier chip near the RX IF port of the transverter. Replacing that seemed to provide significant improvement even without anything else plugged in (e.g. preamps, etc.) I'm guessing I accidentally fried it last time I tried to play with it or something. I also uninstalled the PureSignal port from the HL2 just in case, even though HF seemed fine with it installed.

That said, I'm still not 100% happy with the performance when on its own. For instance, on my Kenwood TM-D700A tonight, I had a nightly net* come in at pretty much full bars while I didn't hear the signal at all in Thetis with the HL2/transverter combo. To figure out how far I'm off by, I first plugged my Elecraft XG3 signal generator into my HL2 and used the level calibration in Thetis (while the XG3 was set to 30 meters and -73 dBm). I then plugged the XG3 into the transverter and set the band to 2 meters. With this setup, Thetis seemed to show the correct signal levels when it was set to -33 and -73 dBm. However, at -107 dBm, Thetis displayed something like -85 dBm instead. I'm not sure if this is related to the performance issues I'm seeing.

Anyway, I'm still open to the possibility it's a configuration issue on my end. Suggestions on other stuff to try would be welcome for sure. If I get time earlier in the day, I'll also check out some signals from sites closer to home and see how those behave.

-Mooneer K6AQ

* For those of you familiar with Southern California, it's the one on the Keller Peak repeater, which from where I live is at least 90 miles and 7000 vertical feet away.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/613315235.1291252.1644292794623%40mail.yahoo.com.

[Roger David Powers]

Anyway, I'm still open to the possibility it's a configuration issue on my end. Suggestions on other stuff to try would be welcome for sure. If I get time earlier in the day, I'll also check out some signals from sites closer to home and see how those behave.

Very interesting.  Yes, knowing more about the signals it could catch would be interesting.

As for other ideas, I'd love to find a decent transverter for a decent price i.e pay more than the Ukranian costs for something more developed, but I think my "widget budget" stays in the general realm of what a HL2 costs.  My skill set is with software and system integration so improving the electronics at the component level isn't something I am likely to do without instructions from someone else.

So I looked at the u2b video https://www.youtube.com/watch?v=aQhkV_0Prao  which is two years old but similar to my use case of interest, digital modes on vhf/uhf. The radio is the off-the-shelf adalm-pluto which has an external rx chain with preamp and tx chain with external amplifier, then bandpass filter and a small yagi antenna.  The main learning point for me is the need to do the coordination of the t/r switching with the application, which he did with an app he wrote himself leveraging gqrx and gnuradio components.  He uses a usb-controlled relay board to switch the components as needed. The other learning point for me is about needing to manage latency, especially if you use FT8 etc which needs you to do tx/rx switching in a timely fashion to hit the next time slot. 

A lot of the things he did were two years ago so might be done differently if he started today.  For instance gnuradio now has both gr-iio and gr-soapy integrated into it.  I imagine going with gr-iio would eliminate one layer of buffering.  Also the 'pluto+' on ebay has two rx and two tx ports so you could chose to dedicate one to the 2m chain and another to the 70cm chain.  It also has gigabit ethernet so you could do larger transfers at a faster bitrate if you wanted to.  It also has a better txco than the standard unit and a port that accepts 10 mhz clock at 3.3v max.  I don't own one of these, but his approach of using a different radio and adding external components to improve its performance is closer to my comfort zone than trying to crack open and improve the Ukranian transverter.

That's just my current thought pattern, but someone could say "just buy the Ukranian transverter and modify it with these parts" and I would be happy to do that myself or ask a local friend to do the mods.  I have a lot of investment in the HL2 ecosystem so would greatly prefer to leverage that.

Regards,

RDP

 

[Kristofer Danner]

I recently received and immediately returned one of the Ukrainian 6m "TCXO series" transverters. It wouldn't receive anything, It just made lots of noise. That Serge guy wanted to just tell me it was normal and I should turn the RF gain down. Total garbage, never again.

I did a preorder for CaribouLite. Hopefully with some amplification and filters that will end up doing everything I want to do above HF. The price is certainly attractive.

KD

[Mooneer Salem]

Additional update -- I listened to some more local repeaters tonight and I noticed that the signal level in Thetis seemed to be the same regardless of whether the coax switch was set to the TM-D700A or to the transverter. (The TM-D700A did properly drop the signal when switched to the transverter.) I'm thinking that there's something behaving like an antenna in my setup.

Anyway, I ordered some nylon screws and nuts from Amazon so I can have the heatsink not be attached to the ground plane, but is there anything else I can check that could be causing that to happen?

-Mooneer K6AQ

--

You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/436b7339-1360-4196-aee6-8aef6e4b1621n%40googlegroups.com.

[Duncan Clark]

In message
<CAAzDfxPAfy3joGi2Z8JezW-O...@mail.gmail.com>,
Mooneer Salem writes

>Additional update -- I listened to some more local repeaters tonight
>and I noticed that the signal level in Thetis seemed to be the same
>regardless of whether the coax switch was set to the TM-D700A or to the
>transverter. (The TM-D700A did properly drop the signal when switched
>to the transverter.) I'm thinking that there's something behaving like
>an antenna in my setup.

Or the switch is dodgy.

Or the front end of the transverter is blown because the switch is
dodgy.

What happens if you connect the antenna straight through to the
transverter?

Duncan
--
Duncan Clark
G4ELJ

[Heikki OH2LZI]

Hello group,

After following the discussion here and elsewhere in the web, I finally decided to order my board (28/50 MHz) from the  Ukrainian vendor.

Looking at the schematic it seems to me that the rx/tx sections are separated physically by a small (33 pF) capacitor and a diode switch which may both fail. Personally I did destroy my first HF RX by applying such a switch in the past! I would certainly consider adding a separate T/R switch with relay and eliminate the capacitor totally. Also the LP filter at the output seems quite simple and may not provide the attenuation of harmonics required. Both the switch and a proper LP filter can be integrated in a small external board. Certainly this requires some extra work, but packing the bare transverter board  properly is a major task anyway. 

I have used relays for T/R in my existing 100% homemade 6-m transverter with no problems. Building a similar device from scratch is, however, quite time consuming and I feel that this Ukrainian gadget would provide a shortcut if properly used and modified as required.  

73 de Heikki (OH2LZI)

[Mooneer Salem]

Hi Duncan,

So, I just tried this now (~10' LMR400UF from the transverter's RF port direct to the window feedthru) and the local repeaters I've tried to pick up thus far have come in much stronger than before. One ham also gave me a "full quieting" signal report after I transmitted. The real test will be the Keller Peak repeater later, of course, but this is promising.

Anyway, it looks like the Diamond coax switches I use share DC grounds across all ports. I wonder if there's some sort of noise coming in over the coax and overwhelming whatever signal the transverter happens to pick up. Perhaps using a different coax switch that doesn't just switch the center pin (if such a device exists) will help? It's interesting that my TM-D700A doesn't seem to have nearly as much trouble going through the same switches (1x for both VHF/UHF radios, then 1x for dummy load vs. outdoor antenna).

Thanks,

-Mooneer K6AQ

--
You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/eOXzBXEYdCBiFw5Y%40ntlworld.com.

[Mooneer Salem]

Looks like Keller Peak is coming in loud and clear here when I have the transverter on the same port as the D700A. Seems like it's time to go to HRO and buy a new coax switch (or repair this one). Thanks for everyone's help!

-Mooneer K6AQ

[Mooneer Salem]

BTW, here's a live screenshot from piHPSDR:

I need to figure out how to get TX working in piHPSDR without frying the RX amp :) (I just had to replace it again because the HL2 somehow used the main Antenna port for TX instead of the low power RX port. This despite having "Disable PA" checked in the XVTR dialog.) However, Thetis seems to behave as intended at least.

-Mooneer K6AQ

[dsolbe...@gmail.com]

I don't have any experience with the dual band transverter but I purchased the 6M one and ran tests with my spectrum analyzer.  The results were not good, in fact they were so bad that I won't operate it on the air.

First the harmonic suppression does NOT meet the FCC Part 97 requirement.  The second harmonic was only down -22db and the 3rd was - 43db.  In addition there was a spur at 56mhz that was only down about -40db.  

I contacted the company and was told that was "normal".

Buyer beware.  

73,

Don K9AQ

[Mooneer Salem]

I have HobbyPCB's bandpass filter (https://www.hobbypcb.com/index.php/products/uhf-vhf-radio/144mhz-band-pass-filter) in front of my transverter to hopefully keep out whatever out of band harmonics I do generate. However, that won't help with the in-band stuff. Honestly, I should probably measure mine despite only having a tinySA here; at least relative measurement should be okay.

On another note, I noticed that Thetis doesn't have a DIGFM mode (similar to DIGU/DIGL). I've been trying to use VARA FM through the transverter and while I can very occasionally ping and auto-tune with local gateways, I can't really connect to them. While I'm sure this isn't a common use case, it would be nice to figure out some sort of way to disable any audio processing that it does while in FM mode to rule that out.

-Mooneer K6AQ

--

You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/0c0692b9-5a5d-4b33-aadb-a15628f2dde4n%40googlegroups.com.

[Roger David Powers]

Their 5W amp for 2m/70cm ( https://www.hobbypcb.com/index.php/products/uhf-vhf-radio/rs-uvpa ) looks like an interesting product.  Probably needs an amp between it and the CaribouLite or ADALM-PLUTO mentioned earlier in this thread.  I just launched a detailed set of questions about that product to them.  Will share anything of interest.

Regards,

RDP

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/CAAzDfxOP2bxtHDxrnOJWScRkAGQW_A5EjfHNyN_ahGgfq-Op0w%40mail.gmail.com.