[amsat-bb] Re: 145 MHz signal blocking 435 MHz downlink

[Greg D]

The more I read about it, the more I expect that the right answer 
depends on one's particular receive-side hardware.  If it's already got 
good out of band filtering, then the hi-pass filter offered by the 
posted diagram won't help, since it's aimed at reducing the 2m 
fundamental overload.  For that, you need to use the 2m port on the Tx 
side (Tx to Common, 2m port to antenna, leaving the 70cm port unconnected).

On the other hand, if the receiver pretty wide open, then the 2m 
fundamental is the main problem, and the posted receive-side design will 
eliminate it before it hits the receive chain.

Yes?

Greg  KO6TH


Jim Jerzycke wrote:
> Since I use a very good 2 Meter bandpass filter on my 2 Meter output, 
> I use the diplexer AT the antenna, ahead of the preamp.
>
> Jim  KQ6EA
>
>
> On 01/20/2014 03:41 AM, Greg D wrote:
>> I know this has been answered before, but I forget.  Given one 
>> Diplexer, is it better to put it on the Tx side to limit the 3rd 
>> harmionic going out, or better on the Rx side to limit the VHF 
>> fundamental coming in?  Tony's diagram shows the later; I would have 
>> thought the former would be more effective (hitting the problem at 
>> its source).
>>
>> Greg  KO6TH
>>
>>
>> Jim Jerzycke wrote:
>>> Yep, been using one of those for years!
>>>
>>> I have a Sinclair Labs unit that provides 100dB rejection outside of 
>>> the 2 Meter band.
>>>
>>> Jim  KQ6EA
>>>
>>>
>>> On 01/19/2014 07:32 PM, w4tas wrote:
>>>> I would also suggest a low pass filter on the two meter transmitter.
>>>> A diplexer will work well for this also.
>>>> This will reduce the third harmonic which is causing your problem.
>>>>
>>>> Good luck,
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message----- From: Jim Jerzycke
>>>> Sent: Sunday, January 19, 2014 2:09 PM
>>>> To: amsat-bb at amsat.org
>>>> Subject: [amsat-bb] Re: 145 MHz signal blocking 435 MHz downlink
>>>>
>>>> Buy a diplexer, and connect it as shown in the linked article:
>>>>
>>>>
>>>> http://www.amsat.org/amsat-new/articles/Mode-J/
>>>>
>>>> I also tilt both of my Yagis so they're 45* to the boom, which makes
>>>> them 90* to each other.
>>>>
>>>> Yes, I lose some signal on terrestrial use, but ti helped cut the
>>>> coupling, and desense, down quite a bit.
>>>>
>>>> 73, Jim  KQ6EA
>>>>
>>>> On 01/19/2014 06:56 PM, Gabriel - EA6VQ wrote:
>>>>> Hi all,
>>>>>
>>>>> I have a coupling problem in my station when trying to work 
>>>>> FO-29.  My 2m
>>>>> signal is completely blocking the 435 MHz downlink, and so I can't 
>>>>> hear my
>>>>> signal off the satellite. I guess it must be something related to the
>>>>> distance between the two yagis. (I use the terrestrial horizontal 
>>>>> yagis you
>>>>> can see at http://www.dxmaps.com/jm19hn.html ). With mode-B 
>>>>> satellites there
>>>>> is no problem.  I have tried it with two different 435 receivers, 
>>>>> and it's
>>>>> exactly the same.
>>>>>
>>>>> Anyone has had this problem o have an idea of the possible 
>>>>> reason?  And what
>>>>> is more important, of some way to solve it?
>>>>>
>>>>> Thanks for any possible help.
>>>>>
>>>>> 73. Gabriel - EA6VQ
>>>>> _________________________________________________________
>>>>> Web-Site: HTTP://www.dxmaps.com
>>>>> VQLog 3.1 (build 78): HTTP://www.vqlog.com
>>>>> _________________________________________________________
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>
>>>> _______________________________________________
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>>>
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>>
>>
>