[VHFcontesting] FN55 - Transverter drive control?

[Duane - N9DG]

Paul's current plan is derived from the approach that I have used in the past that worked very well for 10M IF use. I started with a Vectronics DL300M dummy load, HRO currently lists them at $50. The de-rating graph in its manual suggest it should be good for 100W indefinitely (not sure I believe that). I then drilled a hole under the SO 239 connector to accommodate a BNC. I then connected the BNC via a pi resistive attenuator configuration. Even though the big dummy load resistor didn't match the formula for the shunt input R of a true pi resistive 50 ohm attenuator, it was close enough. And I don't recall the R values I ended up with for the series and output R values, but they were standard R values that were closest to what the pi attenuator calculator called for. When I checked that attenuator it was in the vicinity of 25 dB, which was close to what I was shooting for. I also suspect there may be some capacitive coupling occurring as well. Again having a precision level of attenuation didn't matter for 10M TX IF use, the DL300M modified into an attenuator was good enough.

I then ran the IF radio at around 10-15W TX power. So even a worst case boo boo of hitting it with 100W the transverter would only ever be over driven by 6-8 dB or so. No doubt the transverter output signal would be bad, but I don't think that level of over drive would have let the smoke out either. The reason I picked the 10-15W range was that I also wanted the IF radio TX power to be somewhat  above the lowest level that TX was capable, mainly to keep the desired TX signal well above the quiescent broadband hash of the 10M PA. That broadband hash would find its way into the VHF band TX signal.

At that time I was using Ten Tec Pegasus IFs that were minimally modified to support a split IF. I was in fact running multiple RX IF radios on each of the bands at that time. The N4PY control software allowed configuring the transverter bands such that the TX power control when set to 100% was the 10M 10-15W level that I desired. It all worked very well and reliably.

I have since shifted all the IF radios to PC based SDRs including some HPSDR Hermes boards, they work even better, and are super easy to mate to the transverters.

Duane
N9DG

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On Sun, 2/5/17, Steve Kavanagh via VHFcontesting <vhfcontesting at contesting.com> wrote:

 Subject: Re: [VHFcontesting] FN55 - Transverter drive control?
 To: vhfcontesting at contesting.com
 Date: Sunday, February 5, 2017, 9:43 AM
 
 Paul
 
 Just one more approach....if you can source ordinary
 resistors at a good price you can build your own power
 attenuators for 28 MHz quite easily. It looks like 100 1
 watt resistors would be around $30 from Digi-key, maybe 1/10
 of that from Chinese vendors on Ebay.  Each resistor is
 probably somewhat inductive at 28 MHz, but with enough in
 parallel the inductance is divided by the number of
 resistors and becomes pretty much negligible.  Here's a
 100 W (or so) dummy load using that approach - the SWR is
 great on 10m, but not so good on 6m: 
 
 http://www.qsl.net/ve3sma/HFDummyLoad.pdf
 .  
 
 Occasionally I think about converting it into an attenuator,
 but haven't gotten around to it yet.
 
 73,
 Steve VE3SMA