ICOM 735 & Transverters?
Joe Romanosky
Anyone have any experience/info on using a Icom 735
with a transverter? The 735 manual is skimpy on info
on the transverter jack on the rear panel. any hints
or kinks are appreciated....
I would like to homebrew a transverter(s) for 144 and 220.
73 de K3KN
Erik Skovgaard
Joe,
I tried it using a Hamtronics transmitting and receiving converter. The
transverter output from the 735 is very low (10 mW, I think) - too low for
most transverters. The separate RX antenna input to the 735 is a real
blessing for transverters, however.
I found the sensitivity a little on the poor side on 10 meters. However, a
good preamp on the transverter fixed that (and that is the right way to do
it, too). Overall, the 735 is a very good rig to use on the back end of a
transverter, but you may have to boost the transmit signal. I used the
main antenna output (instead of the transverter output) and an attenuator.
I did manage to blast 100 into the transverter a few times, of course :-)
73 de VE7MDL ....Erik.
Joe Romanosky <say...@erols.com> wrote in article
<32FC2F...@erols.com>...
Gary Coffman
In article <01bc1714$94db0e20$2ec56cce@default> "Erik Skovgaard" <Erik_Sk...@bc.sympatico.ca> writes:
>Joe,
>
>I tried it using a Hamtronics transmitting and receiving converter. The
>transverter output from the 735 is very low (10 mW, I think) - too low for
>most transverters. The separate RX antenna input to the 735 is a real
>blessing for transverters, however.
The output at the transverter jack is much lower than 10 mW. 10 mW is
what most available transverters want to see, but the 735 puts out less
than a milliwatt. The reason for this is that the transverter output is
tapped off the pre-pre-driver stage instead of the pre-driver stage so
the transverter port can be used transceive.
As long as you're going to use the separate Rx input anyway, you can fix
that. The cable going from the pre-driver on the main board to the driver
on the PA board is the right level to drive most transverters. Just unplug
this cable from the main board, and plug the transverter jack cable in its
place. Now you'll have about 10 mW at the transverter jack on the back, but
you can't *transceive* on this port anymore. (That's Ok, you're using the
separate Rx port to receive.)
If you add another jack to the back, you can route the cable going to
the PA to it. Then to restore the radio to normal operation, all you
need to do is put a jumper on the outside on the back between this new
jack and the transverter out jack. Simple. This way you can never over-
drive a transverter, and you'll have the right level for most modern
transceiver designs.
I don't know what Icom was thinking when they set the radio up this way.
Perhaps they had plans, which never materialized, to offer transverters
for it which required the lower drive level. Anyway, after this mod,
it is a wonderful radio to use with transverters.
Gary
--
Gary Coffman KE4ZV | You make it, | Due to provider problems
Destructive Testing Systems | we break it. | with previous uucp addresses
534 Shannon Way | Guaranteed! | Email to ke...@radio.org
Lawrenceville, GA 30244 | |
TIEMANN BRUCE
In article <1997Feb10.1...@ke4zv.atl.ga.us>,
Gary Coffman <ga...@ke4zv.atl.ga.us> wrote:
[An excellent mod for making the IC-735 good for transverters.]
Gary, or anyone else, is there an equally excellent way to modify the
IC-726 (which is IC-725 + 6 meters) for use with transverters?
Has anyone done this?
Bruce
N6URH
Mike Willis
Gary Coffman wrote:
snip |
Great idea Gary, but it defaces the rig. No help when bowwowing Joe's
rig on field day. An easy fix is to make up a small buffer amplifier
using a single transistor, e.g. BF981 or a modamp, operating in a linear
mode (most important) to boost the low power to about 20mW. Then add a
filter on the output to ensure a clean drive.
A level setting pot is a good idea as well so you can adjust the power
input to the transverter, and while you are at it, a relay and two
sockets to switch the receive line and the signal to the transverter
pin on the acc1 connector.
Now you can leave the rig wired for HF and have the transverter
connected. Change bands at the flick of a switch and protect the
transverter from 100W of HF.
73 Mike
Gary Coffman
Well, you can certainly do that, Mike. But 1) I don't consider adding
a jack to the back panel "defacing" the rig, and 2) if I'm borrowing
the rig it only takes a couple of minutes to remove the cover and move
the transverter cable over to the pre-driver output jack, and another
couple minutes to put it back when I'm done. No *permanent* changes are
required. This is the quickest, easiest, and cheapest way to allow the
IC735 to work with 10mW input transverters.
I'd use an external box only if it were imperative that neither radio
nor transverter be touched internally. In that case, your idea is an
excellent one. I'd likely use a MAR-4 as the gain element. Note that
you *could* tuck one of these *inside* the 735 or *inside* the transverter
as alternatives. That wouldn't "deface" either piece of equipment, and
eliminates another external box and another level of TR sequencing.
If you're using transverters with a transceive IF port, the best place
to put the extra amp is inside the transverter on the Tx side *after*
the transverter's internal TR. If you're using a transverter with a
split IF, many are this way, then putting the amp in the radio to bring
it up to "standard" transverter levels might make more sense. Especially
if you want to mast mount the transverter, then having the hotter signal
at the other end of the coax becomes very attractive.
There's nothing *wrong* with your approach, it is just that I'm reluctant
to build yet another box when I don't have to. That's just more stuff you
have to lug along, and another set of cables to add to the tangle, and
possibly cause problems, and another level of TR switching to sequence.
Simon Luttrell
I want to make the suggested mod on my 735 to increase the input level to my 6 metre converter. But where do I find the plug and cable on the main board which I need to swap out for my transverter input? Can anyone please tell me the physical location on the main board or connector J number? (I don't want to connect to the wrong point!). Thanks - Simon - XW0LP
Bill C
> 24 years later.....
>
> I want to make the suggested mod on my 735 to increase the input level to my 6 metre converter. But where do I find the plug and cable on the main board which I need to swap out for my transverter input? Can anyone please tell me the physical location on the main board or connector J number? (I don't want to connect to the wrong point!). Thanks - Simon - XW0LP