[1000mp] Roofing filter and weak sigs

[D. J.]

Dido here too.  Best mod yet.

Dale




On 14, Mar 2005, at 9:33, w2nra at optonline.net wrote:

> Mike,
>
> I have heard that due to an improvement in design the menu 9-1 
> adjustment is no longer necessary.  BTW I have one of the early 
> roofing filters and I concer with everything you say.  My receiver is 
> so quiet now that when I first installed the roofing filter I thought 
> I did it wrong and broke the rig.  I've had this installed for quite 
> some time now and I still think it's great.  Before I always had a 
> background S-1 to S-2 noise level.  After S-0 is the norm.
>
> 73,
> Art
> W2NRA
>
> Mike Schatzberg wrote:
>
>> Hello Vidi:
>>
>> There has been quite a bit written here about the roofing filter.  The
>> archives will be worth a review on this subject.
>>
>> To summarize my experience, the noise floor is reduced by perhaps as 
>> much as
>> 8 to 10 db from my stock Mark V, making it far easier to copy weak 
>> signals.
>> In fact, after reducing the IF gain in menu 9-1 by two numbers, I am 
>> able to
>> read S0 signals Q5.  Following the installation of the mod, my S meter
>> readings were 15 db higher.  A reduction of 3 number reduced the 
>> readings to
>> parity with before the mod readings.  I settled with a reduction of 2
>> numbers, which I felt gave the best signal to noise results for 
>> reading very
>> weak signals.
>>
>> The improvement comes about for two reasons.  The first you have 
>> already
>> stated, the 6 pole 4 khz crystal 1st IF filter in series with the 
>> stock 12
>> khz filter, lets in less noise.  Secondly, the latest production Inrad
>> filters have lower insertion loss, and the two stage low noise 
>> amplifier has
>> a net gain of several db.
>>
>> You will find that the roofing filter mod will accomplish the same 
>> noise
>> reduction that your IF amplifier mod does, but has all the advantages 
>> of the
>> narrower 1st IF filter as well.
>>
>> It is well worth the investment, you will discover a new receiver 
>> when it is
>> installed.  Don't forget to do the Noise Blanker Mod as well.
>>
>> Regards and Happy DXing,
>>
>> Mike Schatzberg
>> WB2AJI
>> ----- Original Message -----
>> From: "Vidi & Hester" <zs6al at cis.co.za>
>> To: <1000mp at mailman.qth.net>
>> Sent: Monday, March 14, 2005 8:02 AM
>> Subject: [1000mp] Roofing filter and weak sigs
>>
>>
>>> Hello everyone
>>>
>>> I took part in the BERU contest using a FT-1000MP with the Inrad 
>>> original
>>> front end mod installed.  I had to deal with a lot of VERY weak 
>>> signals
>>
>> more
>>
>>> so than with  overpowering nearby  stations.  I have read a lot 
>>> about the
>>> advantages of the roofing filter in strong near signal situations.
>>
>> However
>>
>>> I was wondering if the restricted front end bandwidth brought about 
>>> by the
>>> roofing filter will limit the band of total background noise 
>>> entering the
>>> rig and thereby making it easier to pick out signals from in the 
>>> normal
>>
>> low
>>
>>> level of background  noise.
>>>
>>> Bottom line:  Will a roofing filter improve weak signal reception?
>>>
>>> Comments based on experience will be appreciated
>>>
>>> Regards,
>>>
>>> Vidi, ZS1EL
>
>
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