[VHFcontesting] Transverters for Dummies

[David Erickson]

Les,

Well first you need to know a few things about the 2304 transverter.  Does
it have the 10 watt attenuator board in it?  This board also provides a
common IF/relay and 28v relay driver to drive the external relay at 28v. 
Let me take a step back.

When ordering your nice new shiny 222-28, they will ask you a few
questions.  First of all you will probably want the common IF option with
the 10 watt attentuator.  On 222 you will also want the common RF out
relay option as well.  On the microwaves it's external and on 903 and 222
transverters it's internal.

All these same options are pretty much available for all of their
transverters.

So here is what you need to know.  The common IF relay draws up to 25ma at
12v.  This comes out of your rig.  You need to find out what your PTT line
out of your rig can handle.  In our case the TS-2000x can handle up to
20ma.  We ran this way for a long time without incident completely
oblivious.  However when we started interfacing their 3456-144, the
current draw on the relay was higher plus we also needed to key an
external amp so we acquired one of their PTT isolation circuits that Down
East Microwave sells.  This can be keyed by your PTT line and then handle
up to 3amps of current draw on the output protecting your rig's PTT
circuits.  You'll have to look at your Icom's manual to determine what the
max current draw is off of your ptt line.

Then you will need to make up a cable to go from there to the PTT-L input
on the transverter.  PTT-L just means you are pulling the ptt line to
ground to key the transverter.  The transverters can also be keyed with
PTT-H option as well but probably not a good idea in most cases.  Once
your key'ed you can drive RF into it.  On the TS-2000x it has the ability
to delay RF for up to 10 or 20ms when hard keying an external
amp/transverter.  If your ICOM has this option configure it!  It will make
sure you aren't driving RF into the preamp and receive converter in the
transverter before the transmit relay is engadged on the input and output.

So I'd suggest you go back and talk to the guy who graciously loaned you
his 2304 transverter and ask him if it has the 10 watt attentuator or not.
 if it doesn't you'll have to attenuate the RF output from your ICOM down
to the drive level of the transverter.  This attentuator circuit is common
with DEMI and makes it really easy to interface with modern rigs.  The
TS-2000x will not go below 5 watts except on 1296 without messing around
with the rig internally or apply ALC voltage to force the final stage to
drop power further.

Anyhow I hope this has helped.. Good luck and 73's,

Dave W3DIO
http://www.w3dio.org/

> Ok, I confess. Just prior to the VHF June Contest, local guru Jimmy Long,
> W4ZRZ loaned me a very nice Down East Microwave 2304-144 transverter.
> It's equipped with an SMA relay and already adapted for "N" connectors.
> He also supplied me with a nice long loop yagi for the 2.3ghz band. It
> was a wonderful gesture on his part. I stumbled through a "Thank you",
> but didn't have the guts to tell him that I didn't have a clue has to how
> to hook it up and make it work!
>
> I didn't have time to tackle the installation prior to the contest, but
> think I may find time this weekend. I've also since ordered a DEMI 222-28
> transverter for use on the 222mhz band.
>
> My "plan" was to use both of these with an Icom 746Pro that is currently
> not being used for anything else. I'm going to mount the 2304-144 in the
> attic only about four feet from the antenna, hopefully allowing for most
> of it's 1 watt of power to make it into the air. The 222 transverter will
> be in the shack, feeding a Mirage 120 watt amp.
>
> I've downloaded the manuals for each from DEMI, and printed out their
> "Interfacing DEMI Transverters" section too. But truthfully it hasn't
> helped much....
>
> I know that I need to make a connection to the PTT line on the radio,
> most likely from the ACC port on the back, and feed them an RF drive
> signal. DEMI mentions that they make a "DEM Interface" that attenuates
> the 25 watt and separates transmit and receive lines for simple hook up.
>
> My definition of simple and theirs may vary.
>
>
> So, with hat firmly in hand, and red cheeks, I turn to you the collective
> exerts on all this. What the heck do I need to do in order make all this
> work without smoke testing anything! Is there a "transverters for
> dummies" guide on the web somewhere? Anyone else using a IC-746 as their
> transverter rig?
>
> Any and all help appreciated. Next time I promise to just confess
> immediately. Jimmy Long can be a pretty intimidating guy, in my defense!
>
> 73,
>
>
> Les Rayburn, N1LF
>
>
>
>
>
>
>
>
> Les Rayburn, director
> High Noon Film
> 100 Centerview Drive Suite 111
> Birmingham, AL 35216-3748
> 205.824.8930
> 205.824.8960 fax
> 205.253.4867 cell
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