[Premium-Rx] Ten-Tec RX-340 - Amateur Use

Tue Feb 8 11:57:42 EST 2005

Hank, the roofing filter is the FIRST filter after the FIRST mixer. 
Usually, with high IF designs nowadays, they're 40.455 MHz, 60 MHz, or 
something similar.  As you know the first filter after the mixer has the 
most effect on ultimate close-in dynamic range, and these filters are 
usually on the order of 15-30 KHz in bandwidth.  The higher selectivity 
filters (3 KHz, 400 hz, etc) are further downstream at the 2nd, 3rd, or even 
4th IF.  Thus, any crap that passes thru the roofing filter gets amplified 
thru the IF chain and the last filter has the unenviable job of having to 
filter that crap out.   So a strong signal, say 10 KC from your desired 
signal that yuo're trying to listen to on a 4 KC filter is gonna be 
amplified by the IF (and it may be strong enough to drive them non-linear) 
and could even blast thru the last filter if it's strong enough.

Therefore, roofing filters of 10, 6, 3, or even 1 KHz switchable are highly 
desireable, but not necessarily easy to accomplish at the low VHF region 
with crystals.

73 John

----- Original Message ----- 
From: "Henry Kolesnik" <kolesnik at sbcglobal.net>
To: <premium-rx at ml.skirrow.org>
Sent: Tuesday, February 08, 2005 9:39 AM
Subject: Re: [Premium-Rx] Ten-Tec RX-340 - Amateur Use

> It's clear I'm a little behind.  Can someone please explain the difference 
> between a roofing filter and a passband filter and why it's called that? 
> Also what' the difference between selectable roofing filters and passband 
> tuning?
> tnx
>
> 73
> Hank WD5JFR
>
> ----- Original Message ----- 
> From: "Cecil Acuff" <chacuff at cableone.net>
> To: "Carcia, Francis A HS" <francis.carcia at hs.utc.com>; 
> <premium-rx at ml.skirrow.org>
> Sent: Tuesday, February 08, 2005 8:13 AM
> Subject: Re: [Premium-Rx] Ten-Tec RX-340 - Amateur Use
>
>
>>I believe the Ten-Tec Orion has implemented multiple, selectable roofing 
>>filters.  I would imagine it's in the primary receiver though which I also 
>>believe is limited to the Amateur bands only.  I'm not sure the secondary 
>>receiver which is General Coverage takes advantage of that technology.
>>
>> Don't own one though...
>>
>> Cecil...
>> ----- Original Message ----- 
>> From: "Carcia, Francis A HS" <francis.carcia at hs.utc.com>
>> To: <premium-rx at ml.skirrow.org>
>> Sent: Tuesday, February 08, 2005 7:10 AM
>> Subject: RE: [Premium-Rx] Ten-Tec RX-340 - Amateur Use
>>
>>
>>>        I find this quite interesting. I think a prepost filter ahead of 
>>> the
>>> new SDR hardware will be required. The tuned RF stage
>>>    in the R390A does a good job of stripping out wide band crud. 
>>> Multiple
>>> Roofing filters is an option no receivers have yet
>>>    have a big effect on performance. I still think the SDR needs a stage 
>>> of
>>> conversion to an IF with multiple roofing filters
>>> ahead of the bit bashing. fc
>>>
>>> -----Original Message-----
>>> From: Walter (Volodya) Salmaniw [mailto:salmaniw at shaw.ca]
>>> Sent: Monday, February 07, 2005 11:21 PM
>>> To: Williams, Barry
>>> Cc: premium-rx at ml.skirrow.org
>>> Subject: Re: [Premium-Rx] Ten-Tec RX-340 - Amateur Use
>>>
>>>
>>> At 07:20 AM 2/7/2005, you wrote:
>>>
>>>
>>>
>>> Before I went any further I wanted to check and see if any of the RX-340
>>> owners had tried the receiver on the ham bands, particularly in a CW 
>>> pileup.
>>> It would also be interesting to see if anyone has used the RX-340 to 
>>> listen
>>> to a weak AM signal within 10 kHz of a very strong signal.  I did some
>>> listening tests with my HF-2050 and it appears to work pretty well, even 
>>> in
>>> a pileup on 7010.  On the other hand, the filters in the HF-2050 are not
>>> very sharp as compared to modern DSP filters.
>>>
>>>
>>> Hi, Barry.  I have a Ten Tec 340, as well as a HF-2050, an Icom 
>>> 756ProII, a
>>> R390A with a SE-3, and a AOR 7030+ which are often on at the same time, 
>>> so
>>> A-B-C-D-E testing is possible.  Of all these receivers, (and this is 
>>> only my
>>> opinion), the Ten Tec performs the worst on MW with a strong adjacent
>>> signal.  The MW dxers out there are well aware of this fact and have 
>>> gone to
>>> some trouble installing roofing filters to correct the poor performance.
>>> For the longest time, I A-B'd the 2050 and the 340 and virtually in 
>>> every
>>> instance, the 25 year old 2050 out gunned the 340 by a long shot.  I was 
>>> all
>>> set to sell the 340, but it's performance on HF is really very good, and
>>> with ERGO4 computer control, it's a very nice set up.  The 7030+ is an
>>> excellent performer in close, as is the 756, and of course nothing seems 
>>> to
>>> bother the old Collins R390A.  I know several of my MW colleagues have 
>>> added
>>> the roofing filter on the 340 which improves the performance markedly, 
>>> and
>>> they seem very pleased, but at the price of losing the wide audio 
>>> bandwidths
>>> available in the 340..........Walt.
>>>
>>>
>>
>>
>> --------------------------------------------------------------------------------
>>
>>
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>>
>>
>>
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>
>
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