Re: Predicting MW Intermod/Bleedthrough


Russ Edmunds <wb2bjh@...>
 

I lived in Kinnelon and Parsippany for a total of about 13 years, and in Glen Rock for about 6 months, so
I know what you're running into. There are just too many high power stations crammed into too small of
a geographic area, and withhigh ground conducivity coupled with marshland just to make things worse.

Some of what you're experiencing is likely externally generated. Mixing spurs can develop with the audio
from multiple stations showing up on a different frequency. No radio is immune to those since they act
like their own separate transmitters.

Overload on channel or on adjacent channels is a problem with portables because while the smaller
radios seem immune, that may be simply because they have too small a ferrite antenna to be
sensitive enough ( which means they aren't really good AM DX receivers in the first place ).

At the time I lived there ( 1969-82 ) the small portables of the day were largely inferior to the current DSP
chip designs, and the larger portables had decent nulling capability which could be used.

Bottom line, this is going to be an ongoing issue with portables.


Russ Edmunds
15 mi NNW of Philadelphia
Grid FN20id
<wb2bjh@yahoo.com>

AM:  Modified Sony ICF 2010's barefoot
FM: Yamaha T-80 & T-85, each w/ Conrad RDS Decoder;
Onkyo T-450RDS; Tecsun PL-310 ( 2);
modified Sony ICF2010 w/APS9B @ 15';
Grundig G8 w/whip; modified Sony ICF2010 w/whip

--------------------------------------------

On Mon, 9/1/14, schuster@panix.com [ultralightdx] <ultralightdx@yahoogroups.com> wrote:

Subject: [ultralightdx] Predicting MW Intermod/Bleedthrough
To: ultralightdx@yahoogroups.com
Date: Monday, September 1, 2014, 9:15 AM


 









I'm posting this to a couple of
radio-related groups in order to get a wider audience of
collective wisdom. I live in an area of northern New Jersey
that I've come to refer to as RF Alley because of the
concentration of powerful transmitter towers situated in
wetlands a few miles away. The most annoying result of this
proximity is rampant MW intermod and bleed-through on some,
but not all portable radios which can make for frustrating
bandscanning; especially on the upper end of the
band.
Like
many in these forums I've bought many portables over the
years; held on to many and sold or returned others because
of poor performance otherwise, or sometimes just because of
the MW intermod issue alone. I'm getting tired of
playing Russian Roulette with online purchases, and was
wondering how I might predict this propensity ahead of time
- but in spite of reading numerous online reviews before
purchase I often fail because others' experiences doe
not match mine. Can anyone see a predictive
design/architecture pattern here?
SUFFER FROM SEVERE MW
INTERMOD:Tescun Mid-Full Size PLL:
PLL660, 800
Degen Mid-Size PLL: DE-1102,
Grundig/Eton G5/E5
Tecsun Ultralight PLL:
PL-210
Redsun Ultralight PLL: CCrane
SWP
DO NOT
SUFFER FROM SEVERE MW INTERMODSangean Pocket AM/FM PLL: DT
200, 220, 400; ?Ccrane AM/FM Pocket
Sangean Mid-Full Size PLL:
ATS-505, 606
Tecsun Ultralight Analog:
R-9702
Tecsun Ultralight PLL:
PL-200
Redsun Ultralight PLL: Digitech
AR1733 (and so probably the upcoming CCrane
AM/FM/SW/Air)
Sony 1-chip analog ultralight:
SRF-59, etc
Tecsun Ultralight/Medium DSP:
PL-300, 310, 380, 390, 505, 606

Even the "immune" radios are
not totally immune; for instance a local blowtorch at 1010
KHz appears at 1090 on every single radio of every brand,
size, vintage, or design over the years; but I've
learned to live with that.











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