Radiomobile 1070 interference from tool rack !

[Dazza the stag]

Hi all

I have just reinstalled a radiomobile 1070 in my triumph stag. I have read through other threads that discuss similar matters with a heavy steer to problems with the earthing.

What I am not sure on is that the interference I get is when the ignition is on the accessories option, ie the engine isn't running - could that still be an earthing issue ?

I only get it on LW, only decent station is bbc radio 4,Mw seems ok - In fact I can't even get a station on Mw

The other very strange thing (in my opinion anyway) is that if I touch my spanners which hang on the wall with another metal object then that adds further noise to the interference !! And no they are not joined in any way
It also increases if I touch the alloy wheels with a spanner. Just mentioning this in case it provides any clues

Thanks

Darren

[paulsherwin]

Are you doing this in a garage? Old asbestos corrugated roofing panels screen radio signals very well, particularly MW & LW. FM isn't so bad but is still seriously attenuated.

[Nuvistor]

Addition to Pauls comment, have you fluorescent lights or CFL's in the Garage?

[davidw]

Originally Posted by Dazza the stag

I only get it on LW, only decent station is bbc radio 4,Mw seems ok - In fact I can't even get a station on Mw

So you are saying you get nothing,no stations and no interference on MW?
I suspect that you just need to get the car outside in the the clear where the signals will be stronger.

[G8HQP Dave]

Scraping metal together can sometimes create low-level RF interference. The fact that you can hear this tends to confirm that the radio is in a screened situation.

[60 oldjohn]

I presume you have checked the aerial is tuned in to the radio with the small pre set cap?

John.

['LIVEWIRE?']

Have you checked the aerial for electrical leakage between it and ground. Any resistance reading between the centre pin and outer case of the co-ax plug is a no-no. Also check that the outer screening of the aerial cable is actually earthed to the car's metalwork, and for continuity between the centre pin of the plug and the aerial mast. Any problems here will cause poor or no reception and interference.

[Reelman]

....and if you can, check that the centre pin of the aerial plug actually makes contact with the socket. I had a radio where this was not the case, on VHF it worked ok, presumably by capacitive coupling but was very deaf on MW/LW.

Good luck with it!

Peter

['LIVEWIRE?']

Possibly not the cause of the poor reception, though it could be a factor, is that the original 1070 (not the 1070X) uses AF117 Transistors in it's RF/Mixer, & IF Stages. I also recall that sometime in the 70s a batch of Radiomobile Radios, possibly including the 1070 were produced with silicon detector diodes instead of AA119 or similar point contact germanium diodes. The wrong type may also have been fitted as an AGC Diode. These sets were rather 'deaf', so it may be worth checking the diodes, too. Edit - Having re-read the original post, if the radio used to work well in the Stag, the diodes are obviously correct, but one or more of the 117s could be faulty

[crackle]

I have just repaired one of these radios, the AF11x transistors were all faulty, they all worked well after being zapped.
Try tapping each of the AF11x transistors with the handle of a thin screwdriver in turn to see if it crackles.

my method of how I fix tin whiskers; https://www.vintage-radio.net/forum/...19&postcount=5

[Dazza the stag]

Hi All

Many thanks for the replies and sorry for the delay in replying. I am new to this forum and wrongly assumed I would get an email if I got a reply. Thought I was still awaiting approval for the message from a moderator, but logged on to look and all these replies ! Thank you

I feel little silly now when I read NuVistor's post. Given that was the easiest to check I went out this morning without the 6 Fluorescent lights on and 99% of the crackling has gone ! It never even crossed my mind that this could happen.

I can now hear very feint signals on MW too so I will take the car out at the weekend and see if that further improves the signal as it is in a garage at the moment. It doesn't have a corrugated roof but it is part of the house so I suppose there could be other interference around

LiveWire - It is actually a 1070X rather than a 1070 - sorry didn't realise there was a difference

60 Old John - Could you expand on that comment a little as Im not sure what you mean and probably means that I haven't done what you are suggesting

G8HQP Dave - I assume being in a screened situation is a good thing ?

Many thanks all again and I will report back once I have tested it again outside and maybe after I have done what 60 Old John is talking about

Darren

PS - I have now amended my settings so I get notified of any replies

['LIVEWIRE?']

The 1070X is the later model, which uses silicon transistors in the RF * IF stages, so no 'tin whiskers' to worry about. It's otherwise the same as the original 1070. As to 60oldjohn's comment - if you remove the tuning knob and trim, you should see a small hole in the fascia plate. Behind this is the aerial trimmer, which is adjusted (peaked) for best reception on a weak station around 1400-1500kHz (200M)MW. This is done to match the radio to the car's aerial, capacitance wise. All Car radios used to have these trimmers. A small screwdriver is needed for this adjustment, which should be carried out with the vehicle out in the open so that reception is reasonable.

[wireful3]

Darren, being in a screened situation would be a good thing, for setting up with a signal generator. If there are sources of interference inside this screened situation then it would not help.

[60 oldjohn]

Hi Darren, The will be a small hole somewhere on the set with possibly a "Y" symbol I suspect on your set it may be behind the front fascia to enable adjustment with set in place, on the cheap sets the "Trimmer" cold be under set or rear / side. Fully extend the aerial, tune to a weak MW station in middle of the scale, Then with a small 3mm? screwdriver adjust for strongest results.


Hope this helps, John.

Just seen "Livewire" comments.

[crackle]

If you pull the tuning knob off, you will see a crude nut made out of thin metal. Twist this slightly anti-clock wise and it will come away. You should then see a small hole about 1/8th of an inch diameter. Use a narrow blade flat screwdriver, insert it and turn till you feel it locate in the slot. Adjust for best reception on a week station around 200m. Dont use too much force when pushing on the screwdriver, just enough to hold it in the slot of the aerial trimmer.
Mike

[AC/HL]

One post moved to Restoration Services Wanted.

https://www.vintage-radio.net/forum/...d.php?t=104960

[crackle]

Hi Darren
Did you do what was suggested in posts 7 & 8.
Using a digital multimeter on its lowest resistance or continuity range I would check that there is continuity between the aerial element and the centre pin of the plug. Also check that there is continuity between the outer sheath of the aerial plug to the car body.
(You may need a length of wire to extend one meter probe from near the dash to the aerial tip.)
Mike

[Dazza the stag]

Thanks Mike

I can sort of see why my last comment was moved to a new thread but it does sort of spoil the flow of my original thread and it was relevant - apologies to the moderator.

I haven't got a digital meter. I did connect a new earth directly to the radio in case there were any issues with the aerial one and it didn't make any difference. I should have added that since I moved the car out of the garage away from the lights that did improve it significantly.

I suppose I now just want to rule out any problems that may exist with the radio.

Originally Posted by crackle

Did you do what was suggested in posts 7 & 8.

Mike

Just a thought I have an analogue meter, one that I test bulbs and batteries with. So I guess it is the same setting that iI test a bulb with i.e. ensuring that a small current can still run all the way throughout the bulb ?

So I would put one end on the tip of the aerial and then then at the radio end unplug the short aerial lead coming out of the radio, take the cable that it was plugged into and touch the centre of this with the other probe - and I guess like a bulb I should be able to see the current running all the way through

Is that correct ?

And is the above the same as

"Have you checked the aerial for electrical leakage between it and ground. Any resistance reading between the centre pin and outer case of the co-ax plug is a no-no" or is that a different test ?

We all have to learn sometime ! - thanks for your patience

['LIVEWIRE?']

The two tests are basically the same, except that for continuity between any two points you need to set the meter to it's lowest ohms range, whilst for the leakage test it must be set to it's highest ohms range, because, as I said in an earlier post, there must be no readingi.e. an open circuit, between the aerial mast (centre pin of the plug) and the vehicle chasis (outer part of coax plug), whilst there must be continuity - i.e a short circuit between the outer screen of the plug and the vehicle chassis, and between the aerial mast (which, if telescopic, should be fully extended, btw)and the centre pin. An analogue meter will be fine for these tests. In the old days we used to use an AVO 8.

[HamishBoxer]

Having had rubbish performance on a Radiomobile many years ago the fault turned out to be the caps inside the IF transformers.

This could have been the model.