[ICOM] Icom filters question

[V Sidarau]

Hi John,

Indeed, PBT does help, although it is not as efficient as crystal filters.
It's quite logic because PBT is located too late along the RX chain. But for
sure it can suppress some nearby signals or splatters. Moreover, PBT is
flexible.  

I would say, PBT is about suppression rather than selection.

Once again, my opinion is, filters are nothing in respect of fighting SSB
problems we are facing nowadays. The matter is, most of the SSB problems are
on the TX side. If a TX signal is overloaded, distorted or simply overly
strong on the RX side, one cannot escape from products around its freq or
distortions right inside the passband. 
PBT is good enough to suppress a part of these products, and PBT is already
there. Although crystal filters are more selective, the result is not really
worth a respective investment.     

Just MHO.

73,
Vlad VE3IAE

--   




-----Original Message-----
From: Icom [mailto:icom-bounces at mailman.qth.net] On Behalf Of John Geiger
Sent: Saturday, January 30, 2016 10:40 PM
To: ICOM Reflector
Subject: Re: [ICOM] Icom filters question

Hi Vlad,

That is an interesting observation.  The manual talks about how the passband
tuning electronically narrows the passband from either side.  Do you find
that it is enough for SSB?  Also, how does PBT compare to crystal filters in
terms of skirts and ultimate attenuation?

73 John AF5CC

On Sat, Jan 30, 2016 at 6:13 PM, V Sidarau <vs.lists at gmail.com> wrote:

> John,
>
> I for one don't feel any necessity in a SSB filter because in real 
> life they don't help at all. I used to use them in both IC-756 and 
> IC-775. My personal opinion is, SSB filters are just a waste of money. 
> Roofing filters is what really helps in SSB and nothing else. Just 
> save your money and don't buy the SSB filter. You will not miss 
> anything. Then, the 1.8 KHz 3rd IF filter will not suppress any 2nd IF 
> 250 Hz skirts because the remaining parts of skirts at a reasonable 
> level are much narrower than 1.8 KHz.
>
> If you are a serious CW contest operator, you may consider the 250Hz 
> wide
> 455 Hz filter in addition to the 9 MHz one. Otherwise you may easily 
> drop it, too. A single 250 Hz at 9 MHz is quite enough for daily of 
> semi-serious use.
>
> I for one used to use 2 x 250 Hz filters for both CW and RTTY, while 
> the narrow SSB filters were barely used at all. Over 100k QSOs made 
> with such a set-up in CW/SSB/RTTY contesting and DXing.
>
> Hope it helps.
>
> 73,
> Vlad VE3IAE
>
> --
>
>
>
>
> -----Original Message-----
> From: Icom [mailto:icom-bounces at mailman.qth.net] On Behalf Of John 
> Geiger
> Sent: Saturday, January 30, 2016 4:59 PM
> To: ICOM Reflector
> Subject: [ICOM] Icom filters question
>
> I have an Icom 756 original (complete with blue lines in the screen) 
> and want to install both a narrow CW filter and a narrow SSB filter, 
> since I do both modes.  I currently have a FL101 250hz CW filter 
> installed in the 9mhz IF and could get a FL222 1.8KHZ SSB filter for 
> the 455khz IF.  I would use just the FL222 on SSB and use both filters 
> on CW.  So, the 2nd IF would narrow the passband down to 250hz, and 
> the filter in the 3rd IF would maybe narrow it a little more on some
blowby or skirts.
>
> I am wondering, though, if it would be better to have the wider filter 
> in the 2nd IF and the narrower filter in the 3rd IF?  So I could put a 
> FL223 in the 9mhz IF, which on CW would narrow the passband to 1.9khz, 
> and then have the FL53A in the 3rd IF narrowing it down even further.
>
> Would this be a better setup, or doesn't it really matter?
>
> 73 John AF5CC
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