[amsat-bb] Re: Problems with my 9600 baud stuff

James Cottle jim_cott@earthlink.net
Wed Aug 16 10:22:40 PDT 2006

Hi Tom,
  Tnx for your advice. I have now diagnosed several problems 
successfully. 1) I am using RHCP, which makes signals from AO-51 weak, 
complicated by the fact that I have a 15KHz offset which is further 
complicated by doppler and 2) turns out that, when one puts the 910H in 
"satellite mode" the data port receive gets switched as well. This 
morning I was able to copy strong TECHSAT beacons throughout its pass 
and strong voice on ECHO (The passes conflict right now). THanks for 
your guidance. SOmone needs to document this stuff for others!!!! maybe 
on a web page somewhere (in my spare time). Once again you pointed me in 
the right direction. Thanks for the hints. The offset on the 910H is 
well known...what is NOT well known is that, when you get down and dirty 
in there, you cannot adjust it out with the standard XTAL PLL 
oscillator. I have some pretty good test gear here....all of the tools 
but none of the talent (hi hi).

Thomas McDaniel wrote:

> Hi Jim,
> AO-51 is RHCP for voice and LHCP for digital -- I'm using the KLM 
> 435-40CX with the switching relay.  I also find that GO-32 works 
> pretty well using LHCP so I leave my system set for LHCP when I'm 
> working digital.
> I too use a SYMEK (TNC3S) TNC but I don't know about the IC910 hook 
> ups as I use an old modified FT-736.  If you have access to an 
> oscilloscope, you might want to look at the data out of the radio to 
> make sure that it is where it should be.  It seems like I heard that 
> there are separate data ports for each side of the IC-910 -- does sat 
> mode combine them or do you need to use somekind of a "Y" cable for 
> digital sats?  Hook-ups can be tricky.
> I am surprised to hear about the frequency problems, while I haven't 
> used the IC-910, I have had good luck with other Icom equipment.  
> Being 15 KHz off on the UHF band will certainly be a problem tuning 
> the receive -- the data would be outside the passband!  I think I 
> would call Icom service and ask them about this.  If you are using 
> computer control (like SatPC32) you might be able to set an off-set to 
> compensate, but it still shouldn't be that far off -- its hard enough 
> to tune to compensate for doppler shift without an inaccurate receiver!
> 73  Tom  n0ntx
> ----- Original Message ----- From: "James Cottle" 
> <jim_cott@earthlink.net>
> To: "Thomas McDaniel" <tmcdanielsprint@earthlink.net>
> Sent: Wednesday, August 16, 2006 12:10 AM
> Subject: Problems with my 9600 baud stuff
>> Hi Tom,
>>  Thank you for your generous offer. I am using an ICOM IC910h and 
>> interfacing it thru its mini DIN data port to a SYMEK 9600 TNC3. I 
>> was able to get a couple of passes of TECHSAT beacons thru and then 
>> something changed. Now I get no joy on any pass. I believe that I may 
>> have problems with the data port on the 910. I seem to be tracking 
>> the satellites fine, I can hear the downlink voice channels on ECHO 
>> with no problems.
>>   Also, I am running a RHCP M2 432CP30. Is it true that ECHO wants to 
>> see LHCP? I may be seeing a serious degradation in signal strength 
>> due to the mismatch. I have never been able to get a good DCD from 
>> AO-51. I did get a couple of beacons from TECHSAT until something 
>> that I cannot identify changed. I may have switched to the MINI DIN 
>> port thinking it was a more elegant solution.
>>   The frequency accuracy on the 910H is very poor. I tried, in vain 
>> to adjust the PLL and could not bring it in line. So i have ordered 
>> the CR-293 high stability XTAL option, hoping that this will pull the 
>> rig closer to its indicated frequency. It is typically 15 Khz off on 
>> U band and about 40KhZ off on L band. This makes tuning a real 
>> challenge on these short LEO passes. There is not a lot of 
>> documentation available that I have found on problems such as I am 
>> having, so I appreciate your help very much.
>> Jim N6FO

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