[NLRS] 222 ???

[Duane - N9DG]

--- Brent Casavant <bcasavan at tdkt.org> wrote:

> On Wed, 14 Sep 2005, Clair J. Robinson wrote:
> 
> > I have DEMI 2m, 432 and 1296 transverters with 10 watt
> (max) interfaces. I
> > tried playing around with the alc power reduction scheme,
> but I found it to be
> > much too fussy with my FT-990.
> 
> I'll second this.  My DEM 222-28 originally had the 100mW
> drive
> configuration, and I used a TIB to interface it to my
> IC-706MkIIg.  

I too would avoid any scheme that uses ALC to control TX IF
levels. Simply too many ways for it to fail and smoke
something. I went the route that is similar to Clair's by
using a relatively high power attenuator in the TX line fed a
relatively high level of HF drive. I my case I went with
about 20dB of attenation with a semi-homebrew built
attenuator that would handle 20W or so indefinitlty. I feed
the attenuator ~20W on TX. The transverters are all setup for
the 100mW max TX IF configuration. I decided to go this route
because I wanted something that would survive a 100W TX IF
hit and not smoke the transverter, 20 dB seemed to me to be
safe enough as the over drive is only about 6-7dB in that
case. I also felt runing TX IF at 20 watts attenuated down to
100mW helps reduce the relative level of IF radio's broadband
PA noise from being fed to the transverter (i.e a better S/N
ratio for the TX IF signal). As a 100W HF PA will generate a
basically fixed level of of broadband noise whether it is
amplifing a signal to the 20W level or to just the 5W or less
level. 

> I can only picture going back to split TX/RX if I had a
> permanent
> installation, and even then I'd continue to use a
> high-power drive
> because the ALC driver was just too flakey for my comfort.

In my case I've decided to stay with separate RX/TX IF ines
because it makes adding additonal IF RX's quite easy. In my
case for 6&2M I actually have 3 RX's being fed from those
transverters (2 that hear,and one that is exclusively a 
spectrum sweep radio). Once the whole SDR-1000 thing matures
a bit more I can probably simplifiy this some assuming that
it will get the abilty to support multiple RX's within its
sampling passband.

> I'd also inquire as to whether they'll install a better
> power connector
> (e.g. PowerPoles) as the default RCA connector leaves room
> for unpleasant
> error (i.e. touch a live center conductor to the case, blow
> a fuse, find
> that you don't have any spares on hand, and the contest
> starts in five
> minutes -- not that I've ever done that, mind you ;).  I'm
> not sure if
> they'll do this or not, but it wouldn't hurt to ask.

I to despise the RCA's for power connections, I've removed
them from all of my lower band transverters and replaced them
with wire pigtails with my connector of chioce on the wire
leads.

And finally regarding the RX IF gain setting of the
transverter itself I shoot for a IF gain pot setting that
allows me to be able to 'just hear' a distinct rise in
background noise when turning on the transverter with the
transverter antenna connector connected to a dummy load.
Anything more than that degrades strong signal handling
performance. With almost LOS high power (and big antenna)
station like K9NS only some 75 miles or so away from me I
need all the dynamic range I can get when they are
ocasionally boresited right at me while I'm looking in thier
direction.

Duane
N9DG


		
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