Two transverters at once!

Roy Laufer

As some people reading this forum might already know, I have purchased two Downeast Microwave devices - a 2 Meter Preamp/Amp the LDPA 75, and a 70cm 50 watt transverter, to work with my Flex 6700.

DEMI has the 2 Meter LDPA configured so that when shut down, its input is passed thru to the 70cm transverter, so that you can have one or the other, but not both working at the same time.

At first I set it up, with the 2 Meter LDPA into the Flex's XVTR port and the 70cm transverter to RCVR B - that way I can see both bands simultaneously, but I can only transmit on one band.

I thought I might use something like MFJ's crossover antenna coax switch, but these switches are relatively scarce and they are only designed for 0-30MHz frequencies.

After a great deal of detective work I found out that the microwave industry has something called a "failsafe single transfer coax switch" which is just a relay based high bandwidth version of Ham Radio's crossover antenna switch.

Finding one, required another detective job. They are not usually bought by the regular consumer. They sell usually in lots of 5 or more and some of them list for over a thousand dollars! Ebay to the rescue - I found a low power transfer relay going for $40! It should be here in a week or two. When I get an inline switch in place, flicking the switch will swap the XVTR and Rcvr B inputs. I will be able to switch from transmit on 2 Meters to 70cm in seconds!

Perhaps this might give some of you some ideas of how to extend the ability of your Flex Radio!

Good luck!

73,
Roy AC2GS

EA4GLI

Good find Roy.

Would it make sense to have DEMI include this functionality inside of the amp? Or maybe even sell this device? It would be great if the switch is triggered by the TX port that switches on when you TX on UHF. Once and if Flex decides to give us that functionality on future software releases.

Roy Laufer

I am not sure if I would want the transfer switch to energize with each TX - both band's transmission settings on SSDR could be set for XVTR, but in order to Duplex, reception on one of the band's slices must be set to RCVR B and I can't see how to get that to switch back and forth "on the fly" unless you write some software to enable it.

This seems to be an unusual feature to ask for or ask about. Most people MUCH more experienced first asked me "why the heck would you want to" followed by some vague suggestion that I try different "off the shelf" relays until I find one that has enough isolation and not too much insertion loss.

When I asked DEMI about it, their response was "transfer switch, yeah that could work!"

Ebay is a great resource. I looked elsewhere and since this item is primarily used in the Microwave Industry they mark them up heavily and sell them in lots of 5 or greater!

We are either in an incredibly small group of interested parties, or the rest of us has never mentioned it to anyone else???

I wonder if there is a secret handshake required?

EA4GLI

I think we are a very small group indeed, however, I think this will change in the next few years. As we approach a low propagation cycle for HF, and more and more sats are being deployed there might be a renewed interest in VHF and UHF. You and I (and a few more in here) are just getting ready for it early on.

KF4HR

 Roy - your DEM 2M Amp and 70cm transverter sound like they should provide good all-mode performance on those bands for terrestrial work.  As for having two transverters operate at once, is your goal to have both 2M and 70cm both fully operational for satellite work?  If so there are transverters designed for a 28mhz IF, this arrangement (2M and 10M with a transverter), coupled with the Flex FDX Mode should work.  The only missing piece of the satellite puzzle would be to have Flex offer an option (in a future software build) to allow the option to sync two slices together so they track each other (up or down).       

Butch
KF4HR

EA4GLI

Hi Butch, That is kind of the problem, I don't know how you can do it with the Flex. All the transverter options go through the xvtr port. No chance to use either Ant 1 or ant2 as far as i know. I mean, i can always send a 28mhz signal through ant1 or 2 to a transverter, but i will just see 28mhz on the panadapter. Furthermore, 2m uses also the xvtr port for tx.

KF4HR

It's really too bad the Flex 6700 only offers 2M TX to the XVTR port.  If the 2M output could be configured to also output to ANT1 or ANT2 full duplex satellite operation would be simple.  It would just be a matter of setting one slice to 10M and select Transverter for both transmit and receive.  Connect a 70cm transverter, such as the Kuhne Model TR-432H, to the transverter port on the Flex.  This should allow 70cm activity on the 10M panadapter.  Then open a slice on 2M and connect your VHF antenna to ANT1, then activate the Full Duplex Mode (FDX). 

The only other thing missing would be a way to sync two slices to have them track each other (as a typical satellite rig would do), but you could still be able to control the up and down link frequencies manually.   

It's a shame the Flex-6700 is so close to being an excellent satellite radio (too).  I'd love to be able to sell off my satellite radios.  Oh well, perhaps Flex will work this into the mix someday with a future software build.

KF4HR
Butch

EA4AYW

Intending to flex.
If we do not say what we want and how we want to work they never do for themselves.
It's my way of thinking.
I'm also in that situation but a little more complicated, because I have this 6500 and I have to acquire the two transverter.

Tim - W4TME

This is exactly why we established the community.

Ken - NM9P

i think some guys are already doing that using a few splitters and switches, using XVTR, RX1, & RX2 ports.  There was a post about it a few months ago.

EA4AYW

ok