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Author Topic: Transmitter to interface with RSPdx/uno  (Read 286 times)

KK4GMU

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Transmitter to interface with RSPdx/uno
« on: December 31, 2021, 06:50:39 PM »

Is there such a thing as a moderate priced ($200-$500 new) TRX only or transceiver, 10 to 25 watts, with an output to integrate with the RSPdx/uno?  Ideally, band range includes around 40 to 80 meters, plus 2 meters.

Not interested in lots of bells and whistles.  I'd be using it primarily with a Near Vertical Incidence Skywave (NVIS) antenna, among others.
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K7LZR

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Re: Transmitter to interface with RSPdx/uno
« Reply #1 on: January 01, 2022, 08:52:02 AM »

I'm not aware of such a transmitter. I use several RSP units here and was also looking for a nicely matched transmitter.

I've looked at several vintage transmitters i.e. Kenwood T-599 etc. but most of those require manual PA tuning and really aren't suitable for a modern transceive scenario with an SDR.

Another issue is muting and front-end protection of the SDR receiver during transmit. Much has been written about this already but basically it involves shorting (grounding) of the SDR antenna input during transmit, along with interrupting the audio path.

Best option which I've found so far is to use an older transceiver as the transmitter, along with the RSP as the primary receiver. I use mine with an Icom IC-745 and it works great. BUT, that radio was made before CAT control was common and so I must manually tune TX & RX to the same frequency as they cannot be made to track.

Best modern solution within the power and price range that you mentioned is probably the Xiegu G90 transceiver. I had one here for awhile and it worked fantastic with the RSPdx. I only sold it because my interests changed.....

AFAIK there are no transmitters/transceivers with a specific output for use with SDRUno. I think that the Xiegu G90 does have an IQ output but I never used it.


Take care, hope this helps.
« Last Edit: January 01, 2022, 08:57:03 AM by K7LZR »
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KK4GMU

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Re: Transmitter to interface with RSPdx/uno
« Reply #2 on: January 01, 2022, 11:43:59 AM »

Well, I bet there would be demand for such transmitter given the growing popularity and maturing of SDR. There is definite room for entrepreneurial designer in this radio space.
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N6YWU

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Re: Transmitter to interface with RSPdx/uno
« Reply #3 on: January 02, 2022, 10:40:28 AM »

Why to you need something with an output to your SDR receiver?  You could just CAT control any computer connectable transmitter to be on the same frequency as your SDR receiver (maybe plus of minus an XIT offset), and use a relay to ground the receive antenna input.

For builders, for CW and many digital modes, a CAT controlled transmitter could be as simple as an Arduino (or Teensy or Raspberry Pi) connected to a Si5351A synthesizer module (or equivalent) as the stimulus input to an amplifier + filter network.  Don't know of a single kit that does this, but could probably be cobbled together from multiple kits, or maybe a partial build (Tx only) of something like an mcHF kit.
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KK4GMU

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Re: Transmitter to interface with RSPdx/uno
« Reply #4 on: January 02, 2022, 06:59:03 PM »

Something off the shelf and simple would be preferred.

I would like to hear from folks who:
* Use RSPdx/uno or equivalent for their receiver
* On their Windows 10 computer
* And have a moderate-priced transmitter interfaced to it

...to learn how they are all interconnected for seamless operation at least cost.  Not interested in "making" or Arduino or Pi.
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VK6HP

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Re: Transmitter to interface with RSPdx/uno
« Reply #5 on: January 03, 2022, 05:12:54 AM »

What modes do you want to prioritize?  I'm sure that you have a particular need but I don't agree that the stand-alone transmitter would be a widely sort after product, especially outside the experimenter or homebrew sector (where, in my experience, there may be more interest).  More generally, with modern components and architectures it's easier than ever to make a transceiver, and it's not hard to arrive at a receive performance that exceeds that of an RSPdx by a good margin.

But there are always niches outside the mainstream.  For example, I have an RSPdx and I sometimes use it in conjunction with a Zachtek stand-alone WSPR exciter for LF/MF operation.  The Arduino-based exciter drives a homebrew Class D push-pull HexFET power amplifier, which contains the T/R switching needed to safely use the RSPdx receiver.  The receive system runs on a W10 notebook, with SDRuno and virtual audio cables and serial port emulation to interface to WSJT-X.

For a less self-contained but much more flexible operation, I can also replace the Zachtek with the  1 mW transmit "drive" output from my TS-590S or TS-890S transceiver.  However, that's only useful in a couple of test configurations since either transceiver blows the RSPdx out of the water in overall receive performance.

I realize that these examples are not the same use-case you're describing and, if you're interested in relatively low cost, fairly high performance, software defined transceivers you could also take a look at e.g. the Elad range.  Otherwise, the contemporary stand-alone HF transmitter designs that I know of, and which match the performance class of the RSPdx, all sit in the experimenter/homebrew corner.

73, Peter.
« Last Edit: January 03, 2022, 05:22:25 AM by VK6HP »
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KK4GMU

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Re: Transmitter to interface with RSPdx/uno
« Reply #6 on: January 03, 2022, 08:19:29 AM »

What modes do you want to prioritize? 

73, Peter.
2 meter now for my current Technician license; NVIS (Near Vertical Incident Skywave) coverage on the lower HF frequencies (below10 MHz) after I get my General.

This may require two separate transmitters since general use ham rigs don't typically go up to VHF:

One for below 10MHz, such as this: https://www.radioddity.com/products/xiegu-g90-hf-transceiver

And one for 2 meters: Any number of base/mobile transceivers that do 2 meter.  But these don't typically have an I/Q Output for Interfacing with a PC or XDT1 Pan adapter.

Question:  Do most hams who use SDR for "receive" use a transceiver for transmitting that connects to the computer (for what purposes?) or do they just tune their external transceiver's transmitter and computer SDR receiver separately?  Or do the great majority just use the panadapter output on their transceivers to use the waterfall feature of their SDR?
« Last Edit: January 03, 2022, 08:24:06 AM by KK4GMU »
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N6YWU

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Re: Transmitter to interface with RSPdx/uno
« Reply #7 on: January 03, 2022, 09:30:30 AM »

Quote
Do most hams who use SDR for "receive" use a transceiver for transmitting that connects to the computer (for what purposes?) or do they just tune their external transceiver's transmitter and computer SDR receiver separately?

Both.  For HF, I have separate receive and transmit antennas.  Both my Airspy HF+ Discovery SDR receiver on the receive antenna, and my Hermes Lite 2 transceiver on the transmit antenna are connected to my Raspberry Pi 4 (or my M1 Mac).  Since I wrote the SDR software for both, I can set the frequency of both radios to be the same, or I can tune them separately.

My Hermes Lite 2 transceiver has to be connected to a computer to operate it because it has no front panel, just an ethernet jack.

If I wanted to add 2M transmit to my options, I would have to add a transverter to the HL2.
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KK4GMU

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Re: Transmitter to interface with RSPdx/uno
« Reply #8 on: January 03, 2022, 01:53:44 PM »

Alternatively, instead of two separate boxes, one for HF, and the other for UHF/VHF, I've looked at the Yaesu FT-991a, covers HF, VHF/UHF - sometimes called "shack in the box." Ya, ya, $1,100.

Has anyone here used that in conjunction with an SDRuno, and can describe what may be involved in syncing the two?

Or should I just forget about syncing, since the 991a has only one receiver, just use the uno to concurrently monitor another frequency?
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KD7RDZI2

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Re: Transmitter to interface with RSPdx/uno
« Reply #9 on: January 06, 2022, 12:14:18 PM »

Too bad!!! Buy a Drake T4, T4X, T4XB or T4XC. The nice thing is they have a connector for separate receiver with a relay. If you additionally add an RF swichbox with PTT the level of attenuation is a lot, but enough to check your own modulation. The PTT to be used is the two pins connector on the power supply unit (AC4). Sounds difficult but is very easy and rewarding during contests kicking asses to the big 3 fanboys...
« Last Edit: January 06, 2022, 12:19:25 PM by KD7RDZI2 »
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