[ICOM] Re: inrad filters

[Clark Savage Turner]

On Oct 16, 2004, at 5:22 AM, Hart Engel wrote:
>
> I have read a lot of reviews regarding icom radios with inrad filters. 
>  I read that a lot of these filters are not compatible with icom 
> radios.  They don't fit or they make the modulation sound distorted.  
> I say this because, I have read that the same filters the radio uses 
> for receive also uses for transmitting.

Its hard to understand the question, there are many explanations.  I 
have used 30 or more INRAD filters in Kenwood, Yaesu, Ten Tec and Icom 
radios and have never found them a problem.  I have run into some guys 
who drop in a narrow SSB filter and neglect to readjust their carrier 
set point and this can cause an awful sounding SSB signal for sure.  I 
have run into some guys who (I believe this is only true for some of 
the older radios now) didn't like "wiring" the filter in, the INRAD 
replacement was larger than the stock filter and needed to be wired in 
and attached elsewhere inside the radio.  Then, there are certainly 
some defective filters, like for any manufacturer.

"The same filters the radio uses for receive also uses for 
transmitting" ... most radios do this at the main IF.  It makes sense.  
INRAD filters don't really change this about a radio, though some of 
the INRAD "switch kits" allow various combinations of filters in the 
line beyond what is normally offered in the older radios.  Most newer 
radios allow you to choose the filter you'd like to use for 
transmitting (and with the newer DSP radios, you set that filter 
yourself, as you can set your setpoints from the front panel!)

I don't know what ICOM rig you have there, or I could help more.  I 
have the IC-703 here (like the 706) and it uses a 455 KHz main IF, the 
filter Z in/out is the exact same specs as most Kenwood and Yaesu rigs, 
so they all can use the same cheap ceramic filters (made my Murata).  
The INRAD filters could be wired into the rig (if there was room) or 
you can solder an INRAD filter on the board (they are physically 
compatible) as the accessory filter and leave the main ceramic in 
place.  The INRAD filters are usually cheaper and have "better" specs 
than the ones from ICOM, it is really more apparent at the IF's other 
than 455 KHz,  but it is not a big difference to me in most cases.  I 
use the ICOM filter in my little 703 because I found a good deal and it 
is a great filter.  If I had to buy new, I'd get the INRAD to save a 
few dollars and get better skirts by a little.  (And I like the 
proprietor and his company, it is a family operation and George is a 
very helpful guy, you can email or call him and he'll be honest and 
forthright in answering questions.)

>  If this is true, what filters should I be looking for to put in the 
> IF slots as well as the other filter slots for SSB operation for a 
> icom radio?

Depends on your radio and the IF you plan to use.  If it is the 455 KHz 
IF, not much difference, if it is the higher IF, the INRADs offer 
advantages.  If you use the accessory slots, the radio does not use the 
filter for transmit (unless you change something).  Email me off line 
if you'd like to talk some more, I love to discuss this stuff.  My wife 
says I'm a geek, I suppose its true :-)

Clark
WA3JPG