How-To 2m and 70cm DEMI Transverters on a 6700 & Questions

EA4GLI

Still waiting for DEMI to deliver. It seems that we have an extra delay and we will get a newer version of the 2MLDPA

Temporary Delay notice http://01895fa.netsolhost.com/2MLDPA.htm

In the meantime I was thinking on my own setup.

Will it make sense to use a duplexer instead of a Relay Switch?

I am thinking that I can use VHF /  UHF Duplexer connected to the XVRT port of the 6700



For VHF the 6700 will TX out of the XVTR port, go into the Duplexer and send the VHF signal to the 2M amp from DEMI. The return goes back into the Duplexer and back into the XVRT port of the Flex.

For UHF the 6700 will TX out of the XVRT port and into the duplexer HF part, sending the signal into the 28Mhz IF IN of the UHF transverter from DEMI.

The return from the DEMI UHF transverter will go from the 28Mhz IF OUT of the DEMI transverter directly into RX A in the 6700.

This would allow to automatically send the right TX to the right device from the XVRT port of the Flex and allow for Full Duplex without having to manually switch any relays.

Any holes in my reasoning? Thoughts?

EA4GLI

I edited because I made a mess of the first post, put the wrong duplexer image. 

Roy Laufer

I see a significant problem with this. The XVTR will NOT be supplying its 100 mW output at VHF and UHF frequencies - the VHF will be 144-148MHz BUT the 'UHF' will be output at an IF in the 10 Meter range - it will only get upconverted by the transverter itself.

You also need to toggle the two PTT/Drive lines to select which DEMI box is triggered.

If one of your boxes has a separate IN/OUT IF port, you might be able to split the output with an HF/VHF splitter theoretically - it would be interesting if the diplexer loss and other factors would complicate matters...

My transfer switch cost me $39 - that's about the price for a diplexer...

Good luck!

(I read how DEMI ran out of supplies and is redesigning the LDPA as a pure pre-amp/amplifier rather than a part of an older transverter design. The box will be smaller (and colored?) but the maximum power will drop to 50 Watts.)

Mike W8MM

This could be a very nice way to do it.  

It all depends on how much isolation one needs to keep 144 MHz noise and birdies being generated from the 28 MHz IF of the transverter at bay.  Also, I'm unaware of the wide-band spectral purity of the 6700 XVTR output as far as noise messing up any full duplex operation you contemplate.  

If the duplexer doesn't have enough isolation dBs by itself, you could always add 144 and 28 MHz band pass filters after the duplexer to get more isolation.

EA4GLI

I messed up the original post, I edited now putting the right duplexer that separates HF and VHF.

I already purchased the switch Roy, as per your advice.... I was just thinking that with the duplexer it offers fully automated operation, bar the separate PTT lines based on transverter map (which hopefully FRS will implement at one point).

EA4GLI

I found a $10 usb 8 relay board on eBay. thanks for the idea.

EA4GLI

The duplexer offers 50 dB isolation, that seems sufficient ....

EA4GLI

So here is a graphic with the duplexer as distributor of the signals

EA4GLI

This is only feasible in the 6700 that already has 144Mhz out of the XVTR port of the radio.

Bob N7ZO

HI Salvador,

I used this configuration with the 6700 this weekend for the ARRL VHF contest.  Steve at Down East Microwave is now supplying a nice little diplexer with BNC connectors that works well for this application.

Since the TX1, TX2, TX3 outputs are not persisted by band and I did not want to have another switch to change, I just keyed both the LPDA and the L432-28 together and it worked fine.

Eventually, I will need to add some sort of PTT switching to get full duplex for the satellites.  Either that or maybe Flex will add band persistence to the TX output settings.

73, Bob, N7ZO

EA4GLI

Thanks for the info. I just received my diplexer from demi yesterday. I am getting the l432-28 on Wednesday but the ldpa is still a few months from being ready will update my experience with it as I get to use them.

G4NRT

A very interesting discussion and one that gives me food for thought.

I am using three transverters on my 6500. A Spectrum Communications one for 4m and Kuhne ones for 2m and 70cm (actually I am using an HA1YA 2m one until I collect the new model Kuhne one at Friedrichshafen next week).

I have ordered / changed / reworked all three transverters to be dual cable IF.

My plan is to buy one Kuhne's Transverter switches so that I have one set of cables to the switch and then a set to each transverter which I can switch at leisure.  The switch also incorporates a PTT in and out.

Finally, I will be using a variety of diplexers to split the antennas due to only having one SCU in the 6500.

However, the diagrams above give me some other ideas which may work out cheaper or simpler!

This is a great community!

David G4NRT

Simon Lewis

for those switching multiple transverters round on a Flex this might interest you

http://www.w6pql.com/automatic_transverter_interface.htm

Simon Lewis

And if you're using Kuhne boxes .....

http://shop.kuhne-electronic.de/kuhne/en/shop/amateur-radio/converter-transverte/transverter/TR6SW++...

this is interesting as it can be driven from DDUTIL and a USB relay card to select transverter bands remotely

Simon Lewis

and another option for switching .....

https://www.tapr.org/kits_tass.html

G4NRT

This is the solution that I am opting for as I have two Kuhne Transverters.

David

EA4GLI

Things are slowly taking form in my eventual Full Duplex 2m/70cm Flex 6700.
I received the UHF Transverter, 10MHz HUB and Diplexer from DEMI.





This thing is big!!!



Below, 28 MHz span of UHF



This is what working SO50 should look like.

K6OZY

Sorry for awaking this thread, but the back of the 2M amp does not look like that and will not wire the same way.    This is the rear of my amp, minus the antenna ports.  I ordered mine with combined ANT and 75W.  The "XVRT Out" port is only hot if you power off the amp.  I really want full duplex on 2M/70CM for Sat work and am still struggling with a working build by watching this thread.  As soon as we can do it without having to flip a ton of switches physically, I'm ready to order my UHF XVTR.

EA4GLI

I am debating if I should just go the Kuhne route.

http://kuhne.dc-test.de/funk/en/shop/industrial/prof-power-amplifier/prof-vhf-uhf/KU+PA+01401850+HY+...


There is some wording in the DEMI brochure about a USB connection from the amp to the Flex radio, using the flex usb port. I wonder if there will be some mod to the smartsdr software that allows us to make use of the USB port for automation of external devices.



I like the DEMI L432-28HP transverter, it is big but it looks good.... but man, I really don't like the look of the new 2m amp. It is very very ugly. It looks like a cheap eBay UHF amp.




We are talking $400 plus dollars and then the numbers are not great...



17dB gain vs Kuhne's 34db ....



The problem of a year + wait on something is that you start thinking alternatives.....

Mike W8MM

I wouldn't worry about insufficient gain in the DEMI unit.  In fact, I consider "only" 17 dB a plus.   Once the noise-figure cascade has settled down, more gain only hurts dynamic range.  Flex and DEMI have worked together to make a combination of products that give good sensitivity and superior dynamic range. 

With 34 dB of pre-amp gain, one might have to pad the Kuhne pre-amp down with a roll of RG-174 to prevent undesirable IM products during contests ;~}

BTW, I love Kuhne products and use his 432 transverter myself.

EA4GLI

OK, that is a good point Mike... anyone else finds the new enclosure ugly?

G4NRT

Bearing in mind that I only have a 6500 not a 6700, is there a way that I can do full duplex so that I can work satellites?  

Right now I have an Icom IC-910H for that but I'd much rather use the Flex with my two Kuhne Transverters.

The AMSAT paper that I have seen appears to use a whole bunch of switches but I am a little uncertain about which ones and what they do ....

Suggestions on the configuration and what kit I would need would be most welcomed ...

David G4NRT

K6OZY

But back to the wiring question.  Now that you know what the 2M amp looks like, we cannot use the diagram you posted above with this correct?  Is there any way of making a full duplex in either direction configuration?  Most birds require 70CM up while listening to 2M down, so I just can't figure out a way of doing this with the 2M Amp.

George KF2T

Yes, full duplex works fine with the 6500. Use the XVTR port for uplink, and RXA for downlink, with appropriate converters or transverters. I use the Elecraft XV144 and XV432 simultaneously, to separate antennas.

G4NRT

Thanks George.  I shall give that a try ... I will also fiddle about with SATPC32 and see how that goes ... this is what I love so much about this hobby!  There is always something new to try and I still get a thrill making a QSO even after almost fifty years!

David G4NRT 

EA4GLI

Why not? You always TX with the XVTR port and receive with RXA or B. That has not change with the new amp, it only changed the look and output power... And maybe the usb port. I will try to put together a diagram.

K6OZY

On the 6700, you can only TX 2M on the XVTR port, but can listen on to 2M on any port.   The DEMI 2M amp does not have split XVTR ports, thus you have to listen to 2M incoming on the XVTR port also.  This means you cannot use the XVTR port to TX 28Mhz IF to the 70CM XVTR, thus you can't listen to 2M while TX 70CM with the above configuration.  You'd have to get a 70CM XVTR that can accept higher level drive and drive it from ANT1 or ANT2, I assume.

Your diagram assumes the XVTR OUT on the 2M amp is a 2M return at XVTR drive levels.   That is not the case.  It is the radio's XVTR signal passed through the unit while it's powered off.   

From the manual: 
"One feature that is designed for the FLEX transceivers is the XVTR bypass function. When the LDPA is powered down, the XVTR signal from the FLEX XVTR port is bypassed around the amplifier and back out the connector panel."

EA4GLI

hmmm, I thought that is what you could do with the ByPass port, that was the receive loop... but you do have a point if that is not the case.

K6OZY

I think the solution is to not buy the DEMI 2M AMP, but buy a DEMI 2M XVTR just like your 70CM unit, align them both with a 10Mhz signal from your GPSDO.  Then you could wire them up the way you propose above.

EA4GLI

It is clear that it is bypass when the amp is powered down, what I don't know is if it works as the RX of the signal from the antenna when is powered on but it is not getting any RF from the Flex. I guess we will have to ask DEMI.