Transverter Questions 2

dlwarnberg

So round 2 of my transverter questions.  Background.. I built 2 Elecraft transverters (XV432 and XV144), each works individually without issue.  Then following the transverter instructions on hooking them up (Separate receive and transmit, BNC T connectors) so they are both connected

Now both of these transverters are tuned via 28 mhz frequency.  here is what I found:

Slice A XVTR 144mhz
Slice B XVTR 432mhz

Tuning around on Slice 144 found a repeater active and listened, switched to Slice B and started tuning around.. found a repeater active so tuned to it.. to my surprise it was both the same repeater, same conversation yet completely different frequencies and that repeater does not have a 70cm as well as a 2 meter repeater frequency...

WHAT is going on here?  Any idea's?

Stumpted

Thanks
David
KK4QOE

David

Are you using a 6700 or 6500?

dlwarnberg

Flex 6500.. both on RXA for recieve

David

I believe you can only use one transverter at a time connecting to the XVTR BNC, There is only one receiver so if you are using the XVTR you will only be able to listen it and not any of the HF and visa-a-versa. If you had the 6700 which has two receivers and 2m built-in you could then have the 70cm on the XVTR and listen to both. Of course people have setup transverters in different ways to be able to listen to both not using the XVTR port and listen to HF and the transverter by tuning 10 meters which works if 10 is quiet from what I understand. I don't think you have boyh transverters working at the same time in either case but someone else might have another suggestion.

I see you are using the BNC-T connector. Do you have a link on the instructions you used and possibly photos showing your current cabling?

W0DHB

David Ron W5RKN has a recently published article at http://www.flexradio.com/downloads/amsat_jan2016_w5rkn-pdf/ That details how a 6500 transverter setup. Dave W0DHB

dlwarnberg

dlwarnberg

I read it... on the picture of the transverter setup in the XVTR panel does that show one IF frequency at 28mhz and the other at 23mhz or am I seeing things?  FIGURES 4 and 5

Keep in mind, all I'm dealing with right now is receive..

dlwarnberg

Here is an example, this is both the same received stations/repeater

Marc Lalonde

HI  

6500 have 1 SCU  so 1 Transverter RX at the time 

only way to use 2 was use different IF spaced apart whit more that  tranverter bandwidth (28 and 32 as example)  and combine it whit mixer (minicircuit.com) 
then put it on RXA port 

that wly i replace my 6500 by a 6700  

p.s. for SAT work one was in RX and the other one was in TX  in (FDX)
       so none was in RX at the same time  

73!   Marc L. VE2OLM

Duane N9DG

The key thing to be aware of when feeding the IF signals from two different transverters into a single A to D (SCU) is that they will be combined. The IF signals out of both transverters will overlap with each other.

So for example look at these two transverter line-ups hearing these two frequencies:

145.29 – 116 (a very common 2M transverter LO) = 29.29
433.29 – 404 (a very common 70cm transverter LO) = 29.29

So what the above means is that if there is a signal on both 145.29 and 433.29 they will end up directly on top of each other in the IF radio. The same will be true for any other signals across either 2M or 70cm if there IF output from the transverters are the same. The IF radio's single A to D only sees the IF signal in the 10M region. If there are two transverters feeding it signals on 10M they will be “combined”.

And the 145.29 signal will appear in both the 2M and 70cm slice RX's. Likewise the 433.29 signal will too.

Hopefully the above description explains what it is that you are encountering.

All that the transverter setups in SmartSDR (and PowerSDR) do is change what the frequencies are that you see on the displays. The slices themselves are both simply operating on 10M.

One possible way to avoid this is to use transverter IFs that don't overlap. But that is a lot of work because you are now into very custom IF schemes for the transverters, and there is no guarantee that the front end and/or IF output filtering of the transverters will be tight enough to avoid having far out of band (on 2M or 70cm) signals mixing with the transverters LO's and landing in your intended IF ranges.

dlwarnberg

I understand that for SAT work one would be TX other RX... I guess my question is why can't I receive (forget TX) both a 70 cm and a 2 meter signal at the same time?

dlwarnberg

That is what I thought... thank you... so in essence I am receiving both a 70 cm and a 2 meter signal, it's just that they appear on both slices in SmartSDR because I am at a frequency where they overlap.. is that correct?

Thanks

Duane N9DG

Yepp. And as an experiment you can just run the SmartSDR slice(s) on 10M without any transverter configuration set up at all. And you will still hear those same 2M and/or 70cm signals in the 10M band somewhere.

Ron Parsons

David,  
You are correct on the values you see in Figures 4 and 5 in my article.
 
The UHF value of IF=23 MHz is discussed in the Addendum paragraph of the article on page 12.
 
I am confused about your connecting all the RX-IF’s and TX-IF’s in parallel  to all transceivers. You can probably get away with this for receive, but you should not be transmitting into all the transceivers.
 
Another thing to watch out for is when you are using FDX and the uplink IF and downlink IF are within a few kHz of each other. I believe Flex says to keep these frequencies 12 kHz apart in FDX.
 
Ron W5RKN

dlwarnberg

Ron, I was planning on only running a control line or key line to one at a time thus only keying one transmitter at a time via switch... 

Great article by the way and thank you

Ron Parsons

Thanks for the compliment.

I would not recommend transmitting into all transverters even if you "key" only one. I would suggest you contact the manufacturer of your transverters to get their OK before you do it. I did check with DEMI on connecting the RX inputs of their transverters and they approved this, but I did not ask about the TX side. 

Ron W5RKN

dlwarnberg

Will do and thank you again...  I do have them operating on an input of just 1 mw but will fire off a note to them to be sure.

David
KK4QOE

dlwarnberg

was thinking something like this would work..
http://www.amazon.com/Ocean-Matrix-Composite-Expander-Switch-/dp/B00BUG8QF4/ref=sr_1_14?s=electronic...

Ron Parsons

I think you will be happier with a "real" RF coax switch for VHF/HF with 50 ohm impedance and BNC or whatever connectors are on your equipment. The switch you mention above is for composite video use. And looking to the future, you might be planning on how to integrate coax relays for automatic control. FlexSAPC will control relays with a USB-8 relay control board.

Ron W5RKN

dlwarnberg

Reply from Elecraft:
That should work if it is done correctly, since it is possible to daisy chain more than one transverter and have them all connected at the same time.

See: http://www.elecraft.com/XV/XV.htm

Single-port and dual-port IF connections allow use with almost any transceiver. IF transmit levels from -20 dBm to +39 dBm (.01 milliWatt to 8 watts) can be accommodated, with a constant-impedance IF termination for consistent performance. Multiple transverters can be easily daisy chained to a single IF transceiver, providing multi-band operation without cable rearrangement. A brightly illuminated label clearly identifies which transverter is selected.

Ron Parsons

It's good to get the answer from the "horse's mouth." But you can still run into confusion with multiple RX outputs daisy chained to the 6000 RXA port if two bands convert to the same IF, as you realize.

The Elecraft document says "A brightly illuminated label clearly identifies which transverter is selected." How is a particular transverter "selected"? Can you select a particular transverter and energize PTT on them all?

Ron W5RKN

dlwarnberg

Key line to switch, switch out A to one transverter, switch out B to second transverter, switch on side A only transverter A would get the KEY LINE signal to put the transverter in transmit mode, the other would not key... if you want to transmit off transverter B you simply flip the switch.

When I built these transverters they had you make a ground plug (i.e. outter connected to inner)... to key the transverter while alighning you simply placed the plug on the KEY line and the transverter would key to transmit.  The switch would take care of this and isolate one from the key signal.

I hope that made sense.

David

EA4GLI

OK so the amazon Composite switch is just splitting the PTT TX signal from the Flex RCA connector, right?

dlwarnberg

Correct

Ron Parsons

David, I misunderstood that you were using the composite video switch to switch RF. The Amazon switch should work fine to switch PTT and has the appropriate connectors. Cheaper switches for audio would work also fine.

I think  you will find that automating the switching of both RF and PTT is something that you should plan on. FlexSATPC or DDUtil will control a USB-8 relay control board and automate the switching. This can help eliminate "human" errors. I initially used toggle switches and coax switches but I found that even though I was careful, mistakes were made. Safety first, both for yourself and your gear.

Ron W5RKN