[amsat-bb] Re: Tranzit-B telemetry system on ISS

Edward Cole kl7uw at acsalaska.net
Tue Mar 17 00:21:39 PDT 2009

I believe DCI specs their filters on their website.  I have a 6-pole 
144-MHz cavity filter that runs about 0.1 dB insertion loss, though I 
believe they spec it as 0.2 dB.  There are several models so one 
would need the model number.  I use mine between my 1st preamp and 
2nd preamp in my 2m-eme station to help isolate out of band RF 
overload of the receiver.  It is rated for 200w so can be used for Tx 

73, Ed - KL7UW

At 09:57 PM 3/16/2009, Nate Duehr wrote:

>On Mar 16, 2009, at 6:27 PM, Nate Duehr wrote:
> > How are the "American aircraft signals" which are all AM, being
> > rebroadcast
> > in any intelligible way by an FM receiver?
>You know, you didn't say (and probably can't) what kind of receiver
>it's using, actually.  I assumed FM in, FM out.
> > I smell something wrong here with your information, or there's more
> > to the
> > story.
>I was careful to say this, but got one very professional and two nasty
>comments off-list who thought I was attacking the original poster.  I
>wasn't.  The professional comment came (not too surprisingly) from
>someone elected to AMSAT leadership, showing excellent taste and
>restraint.  Thanks, you know who you are.
>Just saying it smelled fishy to me -- assuming an FM receiver.  No
>harm meant by it.  The typical FCC TSO'ed AM aircraft transmitter is
>5W PEP, some are 10W PEP.  5W PEP AM to an FM receiver to be well
>detected at ISS's range is certainly do-able, but it wouldn't sound
>very good, I'd think.  Don't know.  All depends on the receiver
>quality, of course... a bunch of stuff.
>The MUCH more interesting tid-bit that was somewhat hidden in the rest
>of the non-AMSAT info in the message was that there's a DCI filter on
>the front-end of the Kenwood?  Did I read that correctly?
>That made me wonder a new question:  What's the measured insertion
>loss on it?
>It would make for more interesting data for accurate link-budget
>analysis/calculations for talking to the ARISS station.  Would be
>interesting to see if the rig meets the published Kenwood specs, minus
>the antenna "gain" and filtering by altering power from this end and
>seeing if the numbers match up in the real world.
>Is the DCI filter being in-line widely known?  I've never seen it on
>any of the ARISS documentation I've read, but it might have been there
>somewhere.  Maybe I missed it.
>That seemed to be the only AMSAT-related part of that original
>posting...  the fact that there's other "commercial" transmitters and
>receivers on board, seemed like a "given" to me.  It also seemed
>obvious that filtering and mitigation of effects from one system to
>another has to be done, like on all spacecraft or other multi-
>frequency RF systems crammed into a relatively small space.
>Nate Duehr, WY0X
>nate at natetech.com
>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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