2m WSPR Station

2m & 70cm discussion - antennas, propagation, operating, etc
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VK6NI
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2m WSPR Station

Post by VK6NI » Tue Apr 14, 2020 3:07 pm

I've been running a 2m WSPR station here in VK6 over the summer with some good contacts to the east. It is currently an elderly 910H slaved to a PC running 24/7. I plan to continue this but don't see the 910H going on forever and I don't like running a PC 24/7. My current thinking is to replace the PC with a raspberry pi controlling a QRP Labs U3S and linear for transmitting - that's built and working with high stability TCXO and GPS locked. What I need now is a good 2m receiver that I can dedicate to this task.
I can't seem find anything suitable. Using a second hand transceiver or receiver is a possibility but I'm already doing that and it may just give me more problems. I'm happy to build but can't seem to find anything suitable.
Anyone got any ideas, thoughts?
Nigel VK6NI

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VK7HH
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Re: 2m WSPR Station

Post by VK7HH » Wed Apr 15, 2020 10:26 am

Hi Nigel,
Finding a suitable receiver is an interesting one... I can't think off hand what you could use.

Another issue is that because WSPR is one frequency operation, you may have your transmitter going at the same time as your receiver is and you'll have no chance of receiving anyone else. Of course that can be mitgated with a lower transmission percentage I guess

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Re: 2m WSPR Station

Post by VK6NI » Wed Apr 15, 2020 2:57 pm

My intention was to mute/disconnect the receiver during transmission assuming I can pick up a suitable control line from the controlling raspberry pi. My skills with raspberry pi's are elementary to say the least but I am learning.
Nigel VK6NI

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VK5PJ
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Re: 2m WSPR Station

Post by VK5PJ » Wed Apr 15, 2020 4:04 pm

Hi Nigel,
happy to help you with the PI side of things, have two of them running here, one does WSPR on 50.293 with an IC-7100 and the other is a hack toy. The 7100 is not a particularly good choice for WSPR TX as even on 50 MHz I clock up drift values of 4 or more by the receiving stations.

The problems that we all face is that the needed stability at 144 becomes a pot hole to success. I have been using one of the high stability RTL dongles to receive WSPR & JT65 on 144 as an experiment via the PI-4 in the shack. Have not run it for long periods but was surprised at the accuracy of the RX frequency on a few tests. Maybe I should add this to my Covid-19 experiment list :D
Peter Sumner, vk5pj
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Re: 2m WSPR Station

Post by OZ2M » Thu Apr 16, 2020 3:47 am

Hello Nigel

The idea of muting your RX may be a good idea. Another idea could be to place the WSPR transmitter in a different location with remote control - if needed, but a bit more complex. In either case an RFzero https://www.rfzero.net/ can be used on 2 m WSPR and in fact up to 23 cm without using a transverter.

The RFzero S/W is open source so fairly easy to modify for your specific need and make a really smooth setup where all you have to do is to press a button and the RFzero will control the TRX's frequency, muting and prevent it from accidental TXing.

Bo

PS: Shipped two RFzero's to VK5 today (15th) for GHz use.

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Re: 2m WSPR Station

Post by VK5PJ » Thu Apr 16, 2020 8:48 am

Hi Nigel,
as far as RX goes, had GQRX (SDR software) running on my PI-4 overnight and had three good WSPR spots from vk3ot in WSJT-X running on the same PI-4, all reported very similar base band decode frequencies so stability looks good.

The reported decode frequency was slightly off but I have not as yet tried to calibrate the RTL USB dongle. The GQRX software has a setting to allow a PPM (parts per million) value to be set either + or - so will dial in a small value and see if it helps my decodes

https://gqrx.dk/doc/practical-tricks-and-tips

If any of this interests you can send you some screen grabs of what it all looks like. If needed can also send you a ready to go micro SD card with it all pre-loaded as a starting point for you to investigate. As BO mentioned in a previous post you could separate the TX and RX by distance, WSJT-X has the option to not upload self spots so that would not present a problem.
Peter Sumner, vk5pj
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VK6NI
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Re: 2m WSPR Station

Post by VK6NI » Thu Apr 16, 2020 6:45 pm

Thanks Bo for the reply and your RF board looks like a great piece of work. At this point I believe I have the transmit side of things sorted as I described in the original post.

Peter,
Your efforts with reception on a Raspberry pi look like a possible solution. I tried to get a Newgen RTL 2832 with 0.5ppm TXCO dongle that I've had for some time going on a model 3 Pi using the GQRX software but was not successful, not sure why. I've currently got a Nooelec dongle on order out of the US and will give this a go when it eventually arrives. If I'm not successful then I will probably take you up on the offer of writing a micro SD for me. I will also give the Newgen dongle another go when I receive a Pi 4, also on order.
Nigel VK6NI

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OZ2M
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Re: 2m WSPR Station

Post by OZ2M » Thu Apr 16, 2020 7:19 pm

Just a quick couple of comments:
- The RFzero can be used as GPSDO for the RX when not transmitting
- According to Mike, G8NXD, the RFzero is the most stable Si5351A implementation he has seen, and from what I understand he has seen them all

So an RPi (decoder and management) + RFzero (TX + GPSDO)+ dongle (RX) should be sufficient and no extra TCXO etc. is needed.

New thought: during 2 m TX you can even use the dongle RXing on e.g. 6 m and take the LO from the RFzero.

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Re: 2m WSPR Station

Post by VK5PJ » Thu Jul 16, 2020 6:32 pm

Hi Nigel,
if your still looking for a suitable image for a raspberry Pi then you might want to check this one out..

https://www.hamradiodesigns.co.uk/shackpi
Peter Sumner, vk5pj
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Re: 2m WSPR Station

Post by VK6NI » Mon Oct 26, 2020 3:41 pm

Thanks for the info. Finally got around to downloading the free software suite and have had it running on a Raspi 4 for a while. The version of WSJTx was 2.0 so had to update that to 2.2. The other software (which is extensive) in the suite will probably need the same treatment. The Raspi is controlling and reporting my IC910 that is doing WSPR beacon service on 2m across the Bight. All appears to be working well.

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