Tony, your posting couldn’t have been better timed. I can see from Armin’s photo that his XVR is the same transverters.store 28MHz-144MHz transverter (assembled and boxed) as the one I got in the post two days ago to use with my KX2.
So far I’ve tested it only in Rx mode. I’m currently working on a hard-wired PTT solution for CW and SSB modes.
Q1) Did you get the version without the attenuator board in the box as I did. I only now realise the XVR ‘spec’ says 50mW is the maximum input power from the HF rig where as the KX2 minimum output power is 100mW (somehow I thought it was lower). And if so, did you adjust the RV1 pot to reduce the power input to the XVR as the spec suggests?
Q2) I know the SG-Labs XVRs have RF sensing (I have the 23cm version and use it that way) but I could find no reference to a RF sensing method for PTT control in any transverters.store docs. In fact, the set-up instructions say to check very carefully that your HF rig PTT control is correctly wired to the XVR PTT input. So, I’m surprised to read that Tony and Andy (MM0FMF) say it works, on FM at least.
I’m particularly concerned about CW mode where the XVR will be switching rapidly between Rx and Tx mode and if it doesn’t sync properly with the KX2 I imagine one or both could be damaged if both in Tx mode.
I intend to modify a cheap 3.5mm 4-pole jack plug to three RCA phono plugs cable to take the Key Out from the KX2’s ACC socket to the XVR’s PTT input. I would be interested if anyone has used that successfully.
I got the version with the attenuator board built in. The RF sensing is part of the attenuator board. I don’t like the idea of wasting power in a bunch of resistors, but it seemed the safest / least effort route to get going.
I won’t be doing CW in the short term (still learning!), but will try SSB tomorrow with the RF sensing switch (and the antenna the wrong way ). I can see that as per comment above it will be preferable to get a cable to the PTT input in the long term.
Both the KX2 and transverter have instant switching. In the transverter circuit the power is switched between the RX and TX sections and there’s a diode across the RX input that is biased on when the PTT is active.
It should be all lovely-jubbly. Wire the ACC key out from the KX2 to the transverter, KX2 ant to transverter input through an attenuator, transverter ant to the 2m ant. Then VOX on, a bit of delay (I just cannot cope with full QSK) tap the paddle and you should be in business. The KX2 should go into TX, the key out will go low, the transverter will switch into TX almost immediately then the KX2 will make some RF and Bob’s your Uncle. Let go of the paddle, the RF will stop, VOX delay will time out, the key out goes high, the transverter switches back to RX.
The transverter switches the supply to the TX and TX stages with its PTT input and it’s got diodes to protect its front end from its own PA output and there’s another diode to isolate its RX section output from the RF input. It should be happy.
We can assume Elecraft’s designers are capable of walking and chewing gum at the same time so they will have designed their KX2 so the key output goes low always before any RF is produced so whatever is on the key output should get switched over before the RF appears. That all seems fine and dandy.
My only worry is I’d like some kind of resistive 50ohm load between the KX2 and transverter in case the input impedance is something so revolting the KX2 doesn’t like it.
So I’d order their attenuator board and use that so that the system was “proof against activator being cold and damp on a summit and forgetting to set the KX2 output power”; you know you are going to do that at some point. Then you’ll have let all the magic white smoke out of some of the transverter transistors.!
Their board has relays for switching the attenuator pad out of circuit.
I’d stick mine in the post to you tomorrow so you could build up your system on Wednesday. Then you could order an attenuator at leisure and send it to me. But my board is hiding in the shack and I can’t find it. I can’t the Z-match or the bag of T-50/T68 toroids either.
I also have the model with built-in attenuator board and I control my transverter via the acc socket. On the KX 2 you can control the swr to the input of the transverter.
In the transverter mode of the kx 2, I increased the power from below so much that I am at 8 watts output and thus get a clean signal.
At the moment my transverter is on the table and I’m about to install the tcxo as Chris did:
So far it has given me a lot of joy. But it is a pity that there is so little going on ssb.
Nice to read, Armin, that you have a lot of fun with the transverter.
I was able to increase the out power even more by using a short ground connection between the mounting screw and the coaxial socket (see green line in picture).
Maybe it helps
BTW: I first remember hearing this expression from my science schoolteacher. My ears pricked up with alarm and I was thinking, he doesn’t know my uncles, and none of them are called Bob.
Were you QRV last night? Conditions and activity were great. I made 114 QSOs on 2m SSB between 2000 and 2230 UTC, while activating G/SP-015 with 5 watts, an FT-817 and a SOTA Beam.
Condx were rubbish and both Ruhrpott teams Dortmund and “Herne-West” played in the cup (what supposedly was the reason that only few stations from west-DL were on the band).
I had a little dabble in the FMAC and UKAC from G/CE-001 last night. It was great fun. RF sense switching seemed to work fine for both FM and SBB, as far as I could tell.
Despite my earlier concerns about having the “without attenuator” version of the transverter, it seems to be working well.
I tested it on transmit into a dummy load using a hard-wired PTT cable I made linking the Key Out from the KX2 to the PTT input on the XVR. I found adjusting the XVR’s RV1 potentiometer at the IF input had a very non-linear effect on XVR power output. Over a very small adjustment range it went from ~1W (on CW) to about 12-15W. Managed to get a ‘sweet spot’ where the CW output is about 8-10W (as in the photo).
Also, I adjusted the VOX-delay on the KX2 to about 200ms to stop the XVR switching back to Rx between dots and dashes just in case the KX2 and XVR aren’t completely in Rx-Tx sync.
It’s transmitting correctly in CW mode. I tried calling CW and SSB for reports but no luck but had two FM QSOs with good signal and audio reports.
So, the transverter seems to be working well and I’m looking forward to taking it on my next SOTA activation for more 2m-CW and 2m-SSB field testing.
It’s certainly not low budget if you are starting from scratch!
But if you happen to own a 10M rig already, $95 to add 2M is not so bad. (or as little as $35 if you just buy the transverter board)
). I can see that as per comment above it will be preferable to get a cable to the PTT input in the long term.
