BCT15X Sensitivity


Leslie Polt
 

This venerable analog-only model is still being offered new, and I recently purchased NIB from reputable electronics retailer. Primarily for civil/mil airbands. My attic discone feeds the 15X and 3  ICOM receivers (7100, 8500, 8600) through a multicoupler, so all are receiving the same signal. 15 miles from BWI the ICOMs clearly pick up transmissions that the 15X does not hear; even some controllers are breaking squelch with S-5 signals on the ICOMs, the Uniden hears nothing. The same with many aircraft comms; parking all receivers on the same freq. the ICOM misses what the others hear. Close Call is disabled and there is 0 attenuation. Am I overlooking another setting? Using ProScan. Thanks.
Les Polt
Towson, MD.


Leslie Polt
 

Sorry for confusion - the Uniden misses what the ICOMs hear. 
Les


Bernard Skoch
 

Les,

Have you tried swapping multicoupler ports?


Leslie Polt
 

It is a new Stridsberg active multicoupler that is described as providing the same unattenuated signal to each of 8 BNC outputs, so i doubt that changing ports will have an effect. But, no harm in trying.
Les


GM7BNF
 

This mulicoupler, is it buffered by each having an built in attenuator? If not it could be an input impeadance/loading issue.

Try the discone direct to the radio first, then comeback.

Mike



On 10 December 2021, at 13:49, Leslie Polt <ljpolt@...> wrote:


This venerable analog-only model is still being offered new, and I recently purchased NIB from reputable electronics retailer. Primarily for civil/mil airbands. My attic discone feeds the 15X and 3  ICOM receivers (7100, 8500, 8600) through a multicoupler, so all are receiving the same signal. 15 miles from BWI the ICOMs clearly pick up transmissions that the 15X does not hear; even some controllers are breaking squelch with S-5 signals on the ICOMs, the Uniden hears nothing. The same with many aircraft comms; parking all receivers on the same freq. the ICOM misses what the others hear. Close Call is disabled and there is 0 attenuation. Am I overlooking another setting? Using ProScan. Thanks.
Les Polt
Towson, MD.


GM7BNF
 

Put the aerial feed direct to the scanner

 

From: main@Uniden.groups.io <main@Uniden.groups.io> On Behalf Of Leslie Polt
Sent: 10 December 2021 18:06
To: main@Uniden.groups.io
Subject: Re: [Uniden] BCT15X Sensitivity

 

It is a new Stridsberg active multicoupler that is described as providing the same unattenuated signal to each of 8 BNC outputs, so i doubt that changing ports will have an effect. But, no harm in trying.
Les


Don Woodward
 

A question to the multi-coupler supplier would be do all ports present a 50-ohm input/output?  The Uniden could be more sensitive to an unbalanced load.

Don W.
KD4APP


From: main@Uniden.groups.io <main@Uniden.groups.io> on behalf of Leslie Polt via groups.io <ljpolt@...>
Sent: Friday, December 10, 2021 1:06 PM
To: main@Uniden.groups.io <main@Uniden.groups.io>
Subject: Re: [Uniden] BCT15X Sensitivity
 
It is a new Stridsberg active multicoupler that is described as providing the same unattenuated signal to each of 8 BNC outputs, so i doubt that changing ports will have an effect. But, no harm in trying.
Les


Rick NK7I
 

It's unlikely that it's a balance problem, since a scanner works with such a wide variety of antennas; tuned for the bands or not, including a simple whip (where impedance for say, 50 MHz would be WAY off).  It's not generally a place to try weak signal reception (hopefully) where impedance really matters.


It could be a weak/dead port on the multicoupler, failed (if it ever worked) connector/coax to the scanner or a dead receiver.  Reloading the programming (and/or firmware) would be in the list of things to try.  Murphy happens (all too often).


Start simple, does it receive weather broadcasts on a whip antenna? Work up from that.  Try another scanner in it's place.  Follow tests in a logical clear fashion to localize where the problem/s lie.


Merry Christmas,

Rick NK7I



On 12/10/2021 11:32 AM, Don Woodward wrote:

A question to the multi-coupler supplier would be do all ports present a 50-ohm input/output?  The Uniden could be more sensitive to an unbalanced load.

Don W.
KD4APP


From: main@Uniden.groups.io <main@Uniden.groups.io> on behalf of Leslie Polt via groups.io <ljpolt@...>
Sent: Friday, December 10, 2021 1:06 PM
To: main@Uniden.groups.io <main@Uniden.groups.io>
Subject: Re: [Uniden] BCT15X Sensitivity
 
It is a new Stridsberg active multicoupler that is described as providing the same unattenuated signal to each of 8 BNC outputs, so i doubt that changing ports will have an effect. But, no harm in trying.
Les


Rich
 

why not couple the 15X directly to the antenna and see if reception improves?


Matt Levin
 

You may want to try a LNA to boost the signal level.  Each splitter device connected  attenuates the signal level. 

Matt (via iPhone)


On Dec 10, 2021, at 12:49 PM, GM7BNF via groups.io <gm7bnf@...> wrote:



This mulicoupler, is it buffered by each having an built in attenuator? If not it could be an input impeadance/loading issue.

Try the discone direct to the radio first, then comeback.

Mike



On 10 December 2021, at 13:49, Leslie Polt <ljpolt@...> wrote:


This venerable analog-only model is still being offered new, and I recently purchased NIB from reputable electronics retailer. Primarily for civil/mil airbands. My attic discone feeds the 15X and 3  ICOM receivers (7100, 8500, 8600) through a multicoupler, so all are receiving the same signal. 15 miles from BWI the ICOMs clearly pick up transmissions that the 15X does not hear; even some controllers are breaking squelch with S-5 signals on the ICOMs, the Uniden hears nothing. The same with many aircraft comms; parking all receivers on the same freq. the ICOM misses what the others hear. Close Call is disabled and there is 0 attenuation. Am I overlooking another setting? Using ProScan. Thanks.
Les Polt
Towson, MD.


GM7BNF
 

Said this 3 times now….but we get no result.

 

mike

 

From: main@Uniden.groups.io <main@Uniden.groups.io> On Behalf Of Rich
Sent: 11 December 2021 01:59
To: main@Uniden.groups.io
Subject: Re: [Uniden] BCT15X Sensitivity

 

why not couple the 15X directly to the antenna and see if reception improves?


Leslie Polt
 

 No difference trying other output ports on the multicoupler. Unlike a signal splitter, an active multicoupler provides uniform amplification and isolation of all output ports to neutralize signal loss due to a split. Over the weekend I will conduct other A-B comparisons, and report back. Thank you, all.
Les


Rich
 

well, if you have attached the antenna directly to the radio (eliminating the multi coupler and the other radios) amd reception did not improve would that not point to the radio being the likely problem?


Walter Rymarczyk
 

I have a Stridsberg multicoupler, it’s amplified.  I find my 536 works better with the supplied whip antenna than with the discone on the multicoupler.  I think the multicoupler overloads the already sensitive 536.  It works well with my Icom 8500 though.
Walt

Walter Rymarczyk
2650 N Lakeview Ave No 1407
Chicago, IL 60614

On Dec 10, 2021, at 1:49 PM, GM7BNF via groups.io <gm7bnf@...> wrote:



This mulicoupler, is it buffered by each having an built in attenuator? If not it could be an input impeadance/loading issue.

Try the discone direct to the radio first, then comeback.

Mike



On 10 December 2021, at 13:49, Leslie Polt <ljpolt@...> wrote:


This venerable analog-only model is still being offered new, and I recently purchased NIB from reputable electronics retailer. Primarily for civil/mil airbands. My attic discone feeds the 15X and 3  ICOM receivers (7100, 8500, 8600) through a multicoupler, so all are receiving the same signal. 15 miles from BWI the ICOMs clearly pick up transmissions that the 15X does not hear; even some controllers are breaking squelch with S-5 signals on the ICOMs, the Uniden hears nothing. The same with many aircraft comms; parking all receivers on the same freq. the ICOM misses what the others hear. Close Call is disabled and there is 0 attenuation. Am I overlooking another setting? Using ProScan. Thanks.
Les Polt
Towson, MD.


Don
 

*Hi,


I have about 5 different units covering several frequency ranges of the Stridesberg Engineering Multicouplers for many years. There are non-powered or 12vdc powered versions. They produce the same signal level at each port for the powered units. Never have had a problem. Of course these are not just el cheapo rf amps. **
**
**At one time I had thought I would need/like to have a amp/preamp at the antenna(s). I discovered that it is not necessary with the gain of these Multicouplers. In fact an amp on the mast will overdrive the Multicoupler and of course cause problems.**
**
**Anyway, the problem can only be something in the rx, a broken antenna connection in the rx, a bad cable/connector, a bad port on the Multicoupler.**
**
**Hope he reports back. Should be simple to sort out in a couple of minutes.**
**
**Cheers,

Don
*

On 11-Dec-21 02:18, Matt Levin via groups.io wrote:
You may want to try a LNA to boost the signal level.  Each splitter device connected  attenuates the signal level.

Matt (via iPhone)


On Dec 10, 2021, at 12:49 PM, GM7BNF via groups.io <gm7bnf@...> wrote:



This mulicoupler, is it buffered by each having an built in attenuator? If not it could be an input impeadance/loading issue.

Try the discone direct to the radio first, then comeback.

Mike



On 10 December 2021, at 13:49, Leslie Polt <ljpolt@...> wrote:


This venerable analog-only model is still being offered new, and I recently purchased NIB from reputable electronics retailer. Primarily for civil/mil airbands. My attic discone feeds the 15X and 3  ICOM receivers (7100, 8500, 8600) through a multicoupler, so all are receiving the same signal. 15 miles from BWI the ICOMs clearly pick up transmissions that the 15X does not hear; even some controllers are breaking squelch with S-5 signals on the ICOMs, the Uniden hears nothing. The same with many aircraft comms; parking all receivers on the same freq. the ICOM misses what the others hear. Close Call is disabled and there is 0 attenuation. Am I overlooking another setting? Using ProScan. Thanks.
Les Polt
Towson, MD.
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Leslie Polt
 

Interim Report: I tried different multicoupler ports and even the discone feeding 15X directly; as expected, the same results. A signal must be at least S7 on the ICOMs in order to break minimum squelch on the Uniden, and then it's received weakly until it is an S8 or 9 signal on the ICOMs. Interestingly, the 15X "S Meter" shows 5 bars on any signal strong enough to break squelch, so it doesn't seem to serve any purpose. The Uniden specs. indicate AM sensitivity  at .3 mV, whereas the ICOM specs are not better than 1.6 mV (the R7100), so I would expect more from the 15X.  On a lark, I compared the reception of the 15X with a handheld BC125AT/Diamond RH77 whip sitting on the desk, and they received about the same. I would expect far better reception with a desktop scanner and attic discone configuration. With both the Close Call and attenuation features disabled, is there any other setting on the 15X that could be degrading the signal? I have several Uniden handhelds (analog and digital) including the BCD436/536 twins and have been very pleased with them, so this is the first time I've experienced questionable performance in a Uniden.
Les Polt, Esq.
K3JTP


Joe M.
 

Obvious question: How does the 15 compare to the 536?

If there is much of a difference, I
would say there is an issue with the 15.

S-meters, while they at one time were reliable indicators (pun intended), are largely useless as manufacturers make them more sensitive to make the signal appear stronger than it really is.

But an apples-to-apples (Uniden-to-Uniden) comparison seems in order.

Joe M.

On 12/12/2021 11:43 AM, Leslie Polt wrote:
Interim Report: I tried different multicoupler ports and even the
discone feeding 15X directly; as expected, the same results. A signal
must be at least S7 on the ICOMs in order to break minimum squelch on
the Uniden, and then it's received weakly until it is an S8 or 9 signal
on the ICOMs. Interestingly, the 15X "S Meter" shows 5 bars on */any/*
signal strong enough to break squelch, so it doesn't seem to serve any
purpose. The Uniden specs. indicate AM sensitivity at .3 mV, whereas
the ICOM specs are not better than 1.6 mV (the R7100), so I would expect
more from the 15X. On a lark, I compared the reception of the 15X with
a handheld BC125AT/Diamond RH77 whip sitting on the desk, and they
received about the same. I would expect far better reception with a
desktop scanner and attic discone configuration. With both the Close
Call and attenuation features disabled, is there any other setting on
the 15X that could be degrading the signal? I have several Uniden
handhelds (analog and digital) including the BCD436/536 twins and have
been very pleased with them, so this is the first time I've experienced
questionable performance in a Uniden.
Les Polt, Esq.
K3JTP


Leslie Polt
 

A good point; didn't consider it, since I don't have airbands programmed into the 536 (using it for local P25 Phase 1 public service). Will program in a conventional airband system and conduct an A-B comparison since the discone feeds both.  
Les


Rick NK7I
 

Comparing a whip on a desk to an antenna in the attic is not necessarily a valid test.  I have Hardy board siding, which proves to be an excellent RF shield (it's made of concrete, in part).  It's also possible that the losses from the attic are not equal to the losses on the desk (through walls, next to noise sources).

Side by side, sharing the same whip antenna (a tee connector) would be a valid test.  Even moving one whip or being slightly different could place that antenna in a null; make them equal.

As mentioned prior, the arrangement of your system may give the 15x too much signal, overloading it (counterproductive).  A stray voltage may have leaked out from the attic amp causing damage too (if not DC blocked adequately).

The S meter, is useless nowadays, it's a relative meter UNLESS one has taken the time to calibrate it; it's doubtful that Icom did more than a gross calibration (to meet spec, ship it).  As you found, the 15X meter, has no value or usefulness.

After a fair comparison, it's entirely possible that you've lost an element in the 15x making it more deaf, but to be sure, as you are hearing a station, wiggle the antenna connector too and note any differences (one of the weaker points of any radio, easily abused).  Ditto any antenna connection on that feed (you've done part of that by switching ports) and validate the integrity of the cable (chewed on by tiny livestock?).

It may be time for it to be serviced; but when you send it in, try to document what you noted and tested (comparative tests, which band/s tested, types of signals used for the test [AM/NFM/P25], not "it doesn't hear').  You may have a weak or failed amp circuit (blown part or out of tolerance) or it may simply be grossly out of alignment for another reason.  It can happen on new radios or old.

GL es 73,
Rick NK7I


On 12/12/2021 8:43 AM, Leslie Polt wrote:

Interim Report: I tried different multicoupler ports and even the discone feeding 15X directly; as expected, the same results. A signal must be at least S7 on the ICOMs in order to break minimum squelch on the Uniden, and then it's received weakly until it is an S8 or 9 signal on the ICOMs. Interestingly, the 15X "S Meter" shows 5 bars on any signal strong enough to break squelch, so it doesn't seem to serve any purpose. The Uniden specs. indicate AM sensitivity  at .3 mV, whereas the ICOM specs are not better than 1.6 mV (the R7100), so I would expect more from the 15X.  On a lark, I compared the reception of the 15X with a handheld BC125AT/Diamond RH77 whip sitting on the desk, and they received about the same. I would expect far better reception with a desktop scanner and attic discone configuration. With both the Close Call and attenuation features disabled, is there any other setting on the 15X that could be degrading the signal? I have several Uniden handhelds (analog and digital) including the BCD436/536 twins and have been very pleased with them, so this is the first time I've experienced questionable performance in a Uniden.
Les Polt, Esq.
K3JTP


Leslie Polt
 

I conducted an A-B test with the BCD536, which won (although even that scanner does not pick up the BWI ATC the ICOMs receive). Interestingly, both Unidens had the same limited reception until I discovered that the BCD536 "range" had not been set to max., which should be the correct setting for conventional systems. The 15X does not have that feature, and the Close Call was disabled.  Thank you all for your suggestions; it is gratifying to see so many active and helpful participants on this Group.
Les, K3JTP