[ICOM] Re: ICOM IC-775 Roofing Filter

[Anders Janis SM4RNA]

An error

Next, I would go for the 250Hz Inrad for 9MHz IF. Then it is also possible
to use PBT to get any bandwith between 250 and 100Hz or so.


Shold be

Next, I would go for the 250Hz Inrad for __455kHz__  IF. Then it is also 
possible
to use PBT to get any bandwith between 250 and 100Hz or so.




----- Original Message ----- 
From: "Anders Janis SM4RNA" <sm4rna at telia.com>
To: "Skip Cameron" <scameron at austin.rr.com>; "ICOM Reflector" 
<icom at mailman.qth.net>
Sent: Monday, June 11, 2007 9:29 PM
Subject: [ICOM] Re: ICOM IC-775 Roofing Filter


> The roofing filter is not be confused with non rofing filters in the 9M 
> and 445k. (only Ten-Tec'ers do that!)
>
> The 9M and 445k filters are for nerby action and actual bandwith 
> selection. The roofing filter improves the actual receiver preformance by 
> letting less amount of signals in to the mixers, switching diodes, 
> NB-circiut or what ever.
>
> As in your question you state that 2,4kHz is to wide the 9M and 455k 
> filters is what you need. The roofing filter is around 5kHz wide and has 
> nothing to do with close in selectivity to do. I my self, have and I can 
> recomend the Inrad roofing filter but it do not do what you want to 
> acomplish.
>
> The best improvement when it comes to real selectivity on SSB, I find it 
> to be when changing the FL-96 2,7kHz, yes it is 2.7kHz (chek manual and or 
> service manual and www.mods.dk) in the 455kHz IF to a Inrad #109 2,4kHz. 
> It is choosen together with the FL-80 2,4kHz filter in 9MHz IF. (Check 
> Adam Farson's site about this.) It both improves selevtivity and it makes 
> the PBT to get much better.
>
> The next improvment after that would be an 9M 250Hz filter for CW. Then I 
> would choose Icom FL- 101 as Inrad's filter is do not fit and has to be 
> wired in.
>
> Next, I would go for the 250Hz Inrad for 9MHz IF. Then it is also possible 
> to use PBT to get any bandwith between 250 and 100Hz or so.
>
> After that I would consider narrow SSB filters. Actually with the Inrad 
> #109 in the FL-96's place you can use PBT to get the bandwith of your 
> desire, and in real life the IMD of the other's transmitters will limit 
> how close you can get, thereby you will have limited use of narrower SSB 
> filter. But on the other hand, there is place for more filters so why not 
> try? I would go for the Icom FL-223 in the 9MHz IF and an INRAD in the 
> 455kHz IF 2100 or 1800Hz. Probably 2100 as I do think Icom FL-222 that is 
> 1,9 or 1,8 depending up on leafleat, cuts to much of the audio making just 
> hard to copy.
>
> Remember that no mater you buy a bunch of filters or not you still can use 
> the filters you have togher with the PBT and get any bandwith you like. Ok 
> matched filters in a particular bandwith will give you the best (measured) 
> selectivity, but it will not be the thing that decides if you will have 
> the QSO or not.
>
> An option I really would recomend before it is to late is the CR-282 TCXO.
>
> /Anders
>
>
>
>
>
> ----- Original Message ----- 
> From: "Skip Cameron" <scameron at austin.rr.com>
> To: <sm4rna at telia.com>
> Sent: Monday, June 11, 2007 8:32 PM
> Subject: ICOM IC-775 Roofing Filter
>
>
>> Hello Anders:
>> Thanks for the comments!
>> I found at the http://www.qth.com/inrad/ site under Performance 
>> Enhancements that they have a $US
>> 175.00  "ICOM IC-775 Roofing Filter Installation Manual"
>> The curve looks impressive!
>> Would this be preferred as a first improvement, and then the 9mhz 400 and 
>> 2100 roofing filters if I
>> want more improvement later?
>> Skip W5GAI
>> ---------------------------
>> Anders Janis SM4RNA sm4rna at telia.com
>> Mon Jun 11 13:26:01 EDT 2007
>>
>> Roofing filters are in 64MHz IF.
>>
>> If you choose from 9M och 455k the 9m is earlier than 455k in the chain 
>> and
>> therfore to prefere.
>>
>> On the other hand. If you get teh 9M filters at first you will get the 
>> other
>> later or regret that you did not when they are not availeble any more.
>>
>> The DSP filter is 80Hz by the way.
>>
>> /Anders
>>
>>
>> ----- Original Message -----
>> From: "Skip Cameron" <scameron at austin.rr.com>
>> To: <icom at mailman.qth.net>
>> Sent: Monday, June 11, 2007 6:12 PM
>> Subject: [ICOM] Roofing Filters Question
>>
>>
>>>I have an IC775DSP with 455khz and 9mhz IF's.
>>> I have the stock IF filters, which are 500hz for CW and 2400hz for SSB.
>>> On CW I can select wither the 2.4 or the 500, and I can also engage DSP
>>> which really narrows the CW,
>>> down to about 50hz.
>>> For contests and split Dxing, the DSP 50 hz is too narrow on CW, 500 hz
>>> works pretty good, and the
>>> 2.4 is too wide on SSB, with lots of other strong signals interfering.
>>> I have been considering INRAD roofing filters, 400cw and 2100SSB.
>>> Would I need them in both 455 and 9 IF's?
>>> If I just wanted one, not both, which would be best?
>>> Skip W5GAI
>>>
>>
>>
>>
>>
>
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