Alan 42 whistling on channel 4 (PL)

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GusWroclaw
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Alan 42 whistling on channel 4 (PL)

Post by GusWroclaw » 18 Nov 2018, 13:47

Could I bother someone that owns an Alan 42 to switch to the Polish band (PL), remove fthe antenna, turn the squelch down and switch to channel 4? Do you hear a high pitched whistle? Additionally, if you go to channel 3, again without an antenna and put the squelch where it barely shuts off the speaker, and then switch to channel 4 ,does it open the speaker again because of this weird reception at channel 4? In other words does your Alan 42 also seem to be emitting internally something around channel 4 or is it just my radio? Is this normal or should I do something about it? It seems like a very faint signal so usually it's not an issue, but if I want to scan for very faint signals this thing halts my scan on channel 4.
161-TM-313 - Midland Alan 42

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Re: Alan 42 whistling on channel 4 (PL)

Post by rpcomms » 20 Nov 2018, 23:48

Hi Gus
I remember having a older Alan 42 multi model and it did similar thing,I suspect your picking up internal "birdies" from the Micro processor Crystal 4.0 mhz or 4.30 mhz (depending on model version)and its multiplying a harmonic straight on that frequency 26.960Mhz ch3
service manual here http://www.cbradio.nl/alan/ServiceManua ... _Multi.pdf

Maybe ground the crystal to earth plane of pcb maybe reduce it?
I have done that,or adding a copper shield around microprocessor and bonding it to ground internally.
Im unsure if Midland\Alan spray the plastic case internally with special RFI paint to reduce case radiation?
I sent mine back to supplier as wasn't happy with them and annoying birdies in end and same issue scanning would stop all the time.

This is the RF paint ive used on plastic cases to help reduce EMI,RFI issues on cb handhelds with plastic cases.
https://uk.rs-online.com/web/p/shieldin ... s/0568483/

Also without proper test gear it maybe not so easy to track down problem.


Ive ended up with the President Randy II and haven't looked back in build quality and performance and none of these issues.
I know that doesn't help your issue and can relate to your frustrating problem.

I will assume you tried handheld in a different location to rule out strong computer,wifi,power supply local issues?
I cant see that ,but have to ask?

Regards Rob

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Re: Alan 42 whistling on channel 4 (PL)

Post by lambrettadave » 21 Nov 2018, 12:09

I will check my Moonraker major 42 as they are quite similar to the midland 42
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Re: Alan 42 whistling on channel 4 (PL)

Post by The Collector » 21 Nov 2018, 13:16

I've got a Midland 42 and don't even know how to get anything other than EU/UK.

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Re: Alan 42 whistling on channel 4 (PL)

Post by lambrettadave » 21 Nov 2018, 14:03

Dose yours have a am/FM button or a eu/UK button?
CALL SIGN 26TM455 OPERATOR DAVE QTH SUNDERLAND

http://www.flickr.com/photos/88011785@N06/ for CB magazine.reviews

http://www.youtube.com/user/lambrettadave7 for some vids of my radios.

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Re: Alan 42 whistling on channel 4 (PL)

Post by The Collector » 21 Nov 2018, 21:08

Hi have to hold down the LCR button to switch between EU/UK, that's all I know.

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Re: Alan 42 whistling on channel 4 (PL)

Post by GusWroclaw » 23 Nov 2018, 11:15

rpcomms wrote:
20 Nov 2018, 23:48
Hi Gus
I remember having a older Alan 42 multi model and it did similar thing,I suspect your picking up internal "birdies" from the Micro processor Crystal 4.0 mhz or 4.30 mhz (depending on model version)and its multiplying a harmonic straight on that frequency 26.960Mhz ch3
service manual here http://www.cbradio.nl/alan/ServiceManua ... _Multi.pdf
Good catch, It's definitelly in channel 4 for me though, not on channel 3. And channel 4 in the Polish band is 27MHz exactly. So if the chip frequency was close to 4.5MHz, it could it be it. But with 4.3MHz it should have a harmonic at 25.8MHz. Unless you mean that what I hear is the product of the CPU clock modulating another signal in the radio. That could be it.
rpcomms wrote:
20 Nov 2018, 23:48

Maybe ground the crystal to earth plane of pcb maybe reduce it?
I have done that,or adding a copper shield around microprocessor and bonding it to ground internally.
Im unsure if Midland\Alan spray the plastic case internally with special RFI paint to reduce case radiation?
I sent mine back to supplier as wasn't happy with them and annoying birdies in end and same issue scanning would stop all the time.
Well I'm thinking of opening it up and spraying it to see if it helps to be honest. I doubt I'll need the warranty anyway, seems quite sturdy and simply made to crap out on it's own. :-)
rpcomms wrote:
20 Nov 2018, 23:48

This is the RF paint ive used on plastic cases to help reduce EMI,RFI issues on cb handhelds with plastic cases.
https://uk.rs-online.com/web/p/shieldin ... s/0568483/

Also without proper test gear it maybe not so easy to track down problem.


Ive ended up with the President Randy II and haven't looked back in build quality and performance and none of these issues.
I know that doesn't help your issue and can relate to your frustrating problem.

I will assume you tried handheld in a different location to rule out strong computer,wifi,power supply local issues?
I cant see that ,but have to ask?
Yeah the issue happens whether I am in a car, in my house or out in a field. With or without antenna. Pretty sure with any kind of battery as well. The only place where I haven't noticed the sound is in some corners of my house where the electrical noise is was stronger than the whistling signal so
my ear doesn't pick it up, and the scanner doesn't stop on it either.
rpcomms wrote:
20 Nov 2018, 23:48

Regards Rob
Thanks for the answer! I just realized that you people had replied here, I don't know how I missed the notifications. I'll read and reply to the rest in a few minutes.
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Re: Alan 42 whistling on channel 4 (PL)

Post by GusWroclaw » 23 Nov 2018, 11:20

The Collector wrote:
21 Nov 2018, 21:08
Hi have to hold down the LCR button to switch between EU/UK, that's all I know.
In mine I need to hold both LCR and SC (scan) down while turning on the radio. Then press the up arrow button on the side of the radio to select PL. But you probably have a different model. :(
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Re: Alan 42 whistling on channel 4 (PL)

Post by Black Spirit » 23 Nov 2018, 16:03

GusWroclaw wrote:
18 Nov 2018, 13:47
Could I bother someone that owns an Alan 42 to switch to the Polish band (PL), remove fthe antenna, turn the squelch down and switch to channel 4? Do you hear a high pitched whistle? Additionally, if you go to channel 3, again without an antenna and put the squelch where it barely shuts off the speaker, and then switch to channel 4 ,does it open the speaker again because of this weird reception at channel 4? In other words does your Alan 42 also seem to be emitting internally something around channel 4 or is it just my radio? Is this normal or should I do something about it? It seems like a very faint signal so usually it's not an issue, but if I want to scan for very faint signals this thing halts my scan on channel 4.
On my Alan 42 I am getting same thing but a dead carrier which is lighting one bar on s-meter rather than a whistle

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Re: Alan 42 whistling on channel 4 (PL)

Post by Black Spirit » 23 Nov 2018, 16:09

The Collector wrote:
21 Nov 2018, 21:08
Hi have to hold down the LCR button to switch between EU/UK, that's all I know.
With mine when its on UK i can hold down LCR to switch to EC/UK but with radio off if i hold down LCR and SC then power radio on i can let go of the LCR/SC buttons and use UP/DWN to select countries and then press LCR to select the country.

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Re: Alan 42 whistling on channel 4 (PL)

Post by The Collector » 23 Nov 2018, 19:42

Handy to know, cheers Nick.
I only ever use it to test the radios I buy, as there's no bugger round here to get a rig-check off.

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Re: Alan 42 whistling on channel 4 (PL)

Post by GusWroclaw » 25 Nov 2018, 09:54

Black Spirit wrote:
23 Nov 2018, 16:03
On my Alan 42 I am getting same thing but a dead carrier which is lighting one bar on s-meter rather than a whistle
Sounds like in your radio its exactly at the carrier frequency while in mine it's probably a bit off? Though it's not SSB... so I'm not sure how a single frequency a bit off carrier would sound, would it sound like a whistle? Or would the radio be unable to make any sound out of it without a carrier as well?

EDIT: In mine it doesn't light up any bars in the s-meter.
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Re: Alan 42 whistling on channel 4 (PL)

Post by rpcomms » 16 Dec 2018, 22:47

OK best of luck fixing it
You could try and be very careful build a copper tin shield around xtall \microprocessor and solder a short ground wire
On underside use clear tape to insulate
it may help shielding anything from micro or harmonics of CPU xtal
I would suggest earthing the xtal to ground but without a frequency counter it may shift its frequency without you knowing.

If spraying RFI paint just ensure the PCB component parts dont come in contact with the case as they will short to ground,Boom!
You can ground the case via the plastic pcb screw in pillars,thats fine.

If all else fails well and need that band upgrade HT to Randy II or New Randy III soon.

Depends on personal OCD and radio if want things perfect :)

All the best

Rob 73's

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Re: Alan 42 whistling on channel 4 (PL)

Post by GusWroclaw » 14 Jan 2019, 19:11

Thanks for the tips Rob.

First I want to try and make an antenna. I got almost everything but I've been waiting for a more than a month now for some BNC adapters to arrive... :-( I should find a shop here that sells these things. Once I try it out with an antenna I'll see about fiddling with the radio. I don't want to break it before that. :-P
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Re: Alan 42 whistling on channel 4 (PL)

Post by 13EL121 » 22 Jan 2019, 21:14

The Albrecht 2990AFS also has a birdy on 26.995 (CH 3A). Comes from the CPU xtal as expected.
Affects Albrecht 5890 EU as well. Same Family as Midland Radios, maybe same board and CPU design?

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