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

K6OZY

No it doesn't.  It sends the radio's XVTR signal back out that port so you can cascade to another transverter.

EA4GLI

But it does that when it is powered down.... what does the Bypass port do when the amp is on?

K6OZY

It outputs nothing.  I own this amp.

EA4GLI

If DEMI doesn't implement the switch internally then we need to go back to the drawing board and use an external switch, as originally proposed by Roy several months ago... but in this case to switch the return from the 144Mhz antenna to go into RXA or RXB...

I really don't understand why we didn't get a PA for 4m and 2m with the 6700.

K6OZY

Agreed, this makes it really difficult to use the 2M AMP + 70CM XVTR combo for full-duplex Sat work.   This is why I stated above that the answer may be to use a 2M XVTR instead of a 2M AMP.  I'm trying to find out if the 6700 will obey a XVTR definition for 2M overriding its native 2M RX abilities to see if a double XVTR combo would work on it.

EA4GLI

If you go that route the Diplexer will not do much for you so you have to add a switch to send to one or the other transverter... if you are adding a switch, might as well use it for the antenna return and keep the amp.

K6OZY

Another option is that since most of the AmSat birds RX on 70cm, is to simply attach my 2M antenna to RX IN A/B and never transmit at all from it with a 70CM XVTR.

EA4GLI

Another option could be to enabled through a SOFTWARE patch to use ANT1 or ANT2 to TX on 2m.

K6OZY

I think there is a HW block there because it has to go through the radio's PA and filters.

Roy Laufer

I have been following this thread, and following the logic of what goes where could drive the Mad Hatter even Madder!

I have lost track regarding what exactly is the desired result.

To put it simply I have an old DEMI 2M LPNA and a 70cm DEMI Tranverter with a single input/output and a microwave transfer switch.

Presently I can listen to any station on UHF and transmit on the VHF band OR receive on the VHF band and transmit on the UHF band, using my 6700.

Is that the ultimate objective??????

Roy AC2GS

EA4GLI

Pretty much, that is why I mentioned above that all of this to go back to your original design with the external switch.

K6OZY

My requirement is to TX on 70CM while listening to 2M, preferably without any switches or relays on a 6700.   I want to keep it usable remotely without having to deal with that.   I already own the 2M DEMI Amp, so it would need to be integrated into this solution, but I guess could be optional if my goal was ONLY what I said above.  I'd also like to use the 2M AMP on occasion for TX too.

Roy Laufer

My transfer switch is smaller than a pack of cigarettes and gets its power from the same 13.8V source as all my other radio equipment. An inline switch serves my needs, but you may choose to just unplug the transfer switch from its power source. I picked one up on eBay for <$50.

It is the most trouble free setup that I could come up with.

I transmit on my XVTR output and receive on my RX_B input - it seems to work for my needs.

I believe this setup would serve you well, but you are, of course, the final judge for your own equipment.

Vy 73,
Roy AC2GS

EA4GLI

I still have not received my amp from DEMI so maybe they can build it with split IN and OUT

K6OZY

Roy, can you diagram your setup?  I am interested in any setup that works so far with the 2M AMP since I've already invested ~$500 in it.   Can you also show a link to the switch?  Thank you.

EA4GLI

http://www.ebay.com/itm/Ducommun-DB-Products-TA1A31DK-RF-Microwave-Transfer-Switch-18GHz-12VDC-SMA-N...

It was on this same thread further above.

Roy Laufer

...and Salvador drew up a little diagram where all the connections go (this is my exact working setup!)

Steve - K5FR

I'm using this same transfer relay setup and it works very well. Ignore the dotted green line in the drawing and use your own relay switching method. This can all be totally automated.

K6OZY

So Roy, Steve, your 70CM XVTR does not have Split IF?  Salvador's did.

Roy Laufer

Mine does not.

Steve - K5FR

Mine does not either.

K6OZY

OK this why I've waited for so long.   Your switch method makes a ton of sense.  This is the switch in the picture.  It is what you are using for sure:  http://www.ebay.com/itm/Ducommun-DB-Products-TA1A31DK-RF-Microwave-Transfer-Switch-18GHz-12VDC-SMA-N...

Thank you for spending the time working these details out.  The XVTR is a very expensive purchase, and I don't want to buy it with the wrong setup.

Roy Laufer

I understand your trepidations. I drew out the logic diagrams, making sure I was building exactly what I needed. The proof of concept is that it actually works for me! Sometimes you have to re-invent the wheel, and sometimes you get the benefit of someone else sweating the details and sharing with the class. One of the great parts of this hobby is that we all help each other. You don't get much of that with stamp collecting !

EA4GLI

Looks great! I might have to order one of these!

EA4GLI

Well... DEMI informs me that there is no way they can implement a mechanism manual or automatic to switch the signal path between transmit and receive on the 2M amp. They said they "require an addition of 3 relays or PIN diode switches within the 2MLDPA" for the amp to do what we need. I have no clue why... but I they say so....

This puts a dent in my plan and makes me reconsider the DEMI purchase.

Integration with Flex 6700 was a big PRO of the DEMI. Without that I do not see why wouldn't I purchases a Kuhne or any other brand if I have to manually switch the return path of my antennas.

It is very frustrating and expensive to try to make this radio work in VHF or 4m for that matter.
Not a very happy camper at the moment....

The main reasons to have 2 SCUs was, in one hand, diversity, (which is very rudimentary in SmartSDR right now) and on the other hand being able to work Full Duplex which is useful for Sat work. But then the whole VHF and transverter part of the 6700 is just not ready. You should have 2 XVTR ports out of the back of the radio because you have 2 SCUs... but that is not the case which limits things. I imagine people use the Loop ports for something, two of them... there has to be a reason to have those there....but I think 2 x XVTR would have made more sense. Two 6300 will actually give you more play... but you can't have both running on the same PC, because you can't have 2 instances of SmartSDR running on the same PC.

There are just a lot of holes right now....

I understand I can use external switches, and that I can automate with external relays... I can also use a Kenwood TS2000 for the SATs and a $150 SDRplay to RX.

EA4GLI

And even worst.... you could actually work Sats on Mode B with transverters for 144MHz having Split IF which makes having 144MHz out of the 6700 a disadvantage over the 6500. Oh well.

K6OZY

I'm glad we were able to figure out this before you got that amp.   I have committed an order for a 70CM unit from DEMI built with a common IF and ordered that switch off eBay too.   Since I already have the 2M amp for other uses (FM Repeater and SSB stuff), I'm already invested.

I also confirmed that with the 6700, even if it has 2M natively, can still use a transverter for 2M on it to override the native 2M support.   This will let the 6700 behave just like the 6500 on that matter.

EA4GLI

But... isn't there a way we could make use of the 2 SCU and get 2 XVTR ports?

G4NRT

I have given up on trying to make all this work with transverters on my 6500.  I have sold my Kuhne transverters and used the money to buy an IC-9100 which plays perfectly well with SatPC32 and all the other applications I want to use.  

In the end discretion was the better part of valour (as we say on this side of the pond!).

David G4NRT

Steve-N5AC

With SmartSDR v1.10, we will be introducing the capability of adding cables to the FLEX-6000 that will provide CAT and/or BCD/binary outputs.  The system is quite flexible and we'll do a post on this soon, but I wanted to point out a couple of products that Downeast Microwave has that will allow simultaneous, full-duplex 144/432 operation on the FLEX-6700.  The first is the DEMI LDPA (low drive power amplifier) which can be found here: http://www.downeastmicrowave.com/product-p/2mldpa.htm  This amplifier will put out high power on 2m from the low output on the FLEX-6700.  If you order the LDREM-OPT with this, the unit will ship with a USB cable that plugs directly into the FLEX-6700 which will allow complete automatic and/or remote control of the LDPA from SmartSDR.  

The second one is a new switch/diplexer that allows operation of a 432/28 transverter in conjunction with the LDPA, model name DIPS: http://www.downeastmicrowave.com/product-p/dips.htm.  With both of these and a 432/28 transverter you can have a full-duplex 144/432 station for satellite or terrestrial operation.  The DIPS PDF above shows how to connect the system.  We expect to have a more complete description on how to do this including the software setup in the next few weeks.