Topband: Modification to INRAD Roofing Filter
bm at broadcast.se
Sun Oct 21 04:56:32 EDT 2007
Dennis W0JX wrote:
> Those of you who have the INRAD Roofing Filter Kit in your 1000MP's might
> in the following modification to improve the IMD numbers reported by W8JI:
Dennis & topbanders,
Interesting, the question worth raising is; why did I install the roofing
filter to begin with? Looking at the numbers it seems like the NB mod was
all needed to bring the performance up. Doing the suggested roofing filter
mod will bring the numbers "back" to what would be expected after doing the
NB Mod. To me it looks like removing the roofing filter is an equally good
fix, or isn't it?
>From W2AJI's mod:
> Pretty interesting, notice the rather dramatic improvement in close
> and BDR when the Inrad mod is removed. I suspect that this will be true
> spacing within the bandwidth of the filter. Now, I also suspect that the
> bandwidth is actually wider than the advertised spec of 4 KHz, more like
> between 5 and 6 KHz.
I also have the Inrad IF mod, and reading this I am actually considering
replacing the roofing filter for this mod. In addition to topband, I do a
lot of DXing on higher bands where it might do some difference. Are there
any side effects with the IF mod that I should consider?
73 de Björn /SM0MDG
Från: topband-bounces at contesting.com [mailto:topband-bounces at contesting.com]
För Dennis W0JX
Skickat: den 20 oktober 2007 20:54
Till: topband at contesting.com
Ämne: Topband: Modification to INRAD Roofing Filter
Those of you who have the INRAD Roofing Filter Kit in your 1000MP's might be
interested in the following modification to improve the IMD numbers reported
The mod was developed by Mike, W2AJI. It apparently reduces the gain a
little in the roofing filter 2 stage amplifier.
I have not yet tried the modification but it looks simple, involving the
change of only two resistors.
I also believe, as does Mike, that the filter is actually a little wider
than the specifications state. I have no trouble copying AM stations on my
main rx. The filter kit I have is my second one due to a failure of the
filter in my first kit purchased two years ago. The bandwidth of the first
kit seemed a bit tighter than the one I presently have but it is still an
improvement over the stock radio.
73, Dennis W0JX/8
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
Topband mailing list
Topband at contesting.com
More information about the Topband