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TOPIC: TM271A Kenwood receiving problem - LOW Sensitivity

TM271A Kenwood receiving problem - LOW Sensitivity 9 years 3 months ago #371

Salaam,

My tm271a for some reason has very low sensitivity on receiving a signal. I am from Indiana area and the murree romeo return signal is only 5/5. My setup is a 20ft pole with an F22 on roof, the antenna setup is perfect as when I connect my hand held to it or the other base, I get excellent reception but when I connect the Tm271A, it only receives 50% strength.

I searched the internet and found ;

" it may indicate that you are running an antenna that is not DC grounded and static charges/nearby lightning and such are punching holes in the first RF stage FET transistors. This is usually exhibited as slowly failing sensitivity rather than a "sudden death" situation.

Also, the installed rig will be attached to that antenna 24/7 in most cases and may well mean that an antenna with no DC ground on it can be free to transfer static charges to that poor FET input transistor the whole time..."


www.eham.net/ehamforum/smf/index.php/topic,69279.0.html


please advise as I donnot have any grounding of the wire mash but I had grounded the pole on which the antenna is fixed. We did have thunderstorms and lightning in Indiana area in the past weeks.

73's,
A simple Hammer ;)
When All Else Fails !!
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Re:TM271A Kenwood receiving problem - LOW Sensitivity 9 years 3 months ago #372

  • Riffad Khan AP2RF
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AOA

Your receiver probably lost its front end section , i.e. Ant SW , BPF or Signal Amplifier – 3SK318 .

I think the problem comes through 220V AC Line .

I have attached the radio service manual for your convenience.

If you need any further help kindly don’t hesitate to contact me.

73s

Riffad -AP2RF

Attachment TM271_SM.pdf not found

Muhammad Riffad Khalid
AP2RF
Last Edit: 9 years 3 months ago by Riffad Khan AP2RF.
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Re:TM271A Kenwood receiving problem - LOW Sensitivity 9 years 3 months ago #373

Dear ap2rf,

Thankyou for your reply, Please intimate how may I acquire the required component and its replacement.

73's,
A simple Ham'r ;)
When All Else Fails !!
Last Edit: 9 years 3 months ago by Simple Ham'er AP2CJ.
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Re:TM271A Kenwood receiving problem - LOW Sensitivity 9 years 3 months ago #374

  • Riffad Khan AP2RF
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AOA

Open service manual and go through below steps.

1)Check Antenna Switching Diodes , D602 , D603 & D605

2) Check BPF , D353 , D354 , L356 & L357

3) Check RX AMP FET Q353.

A more simple & easy tip

Unplug your antenna PL-259 from radio , take 2 short cables . one wire to Connect one end to the antenna Ground and other with radio ground.

Attach second short wire with the centre leg of PL 259 and solder other end of wire with the leg of a jumper resister (0ohm) or .01ohm .

Connect / attach ( NO SOLDER ) that resister on each stage one by one as described in points 1 , 2 and 3 while clicking Romeo from your handy and check where your signal improves.

the point where you get full signal that mean the previous stage was faulty.

You can also try to connect that resistor directly at the Gate & Drain of Q353 to confirm the fault.

Hope that helps.

73s

RF
Muhammad Riffad Khalid
AP2RF
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Re:TM271A Kenwood receiving problem - LOW Sensitivity 9 years 3 months ago #377

im sorry for the late reply, thankyou RF for all your help.
When All Else Fails !!
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Re:TM271A Kenwood receiving problem - LOW Sensitivity 9 years 2 months ago #378

I believe my set is cooked for now as the required components nor the pcb as suggested is available :(

thus this simple ham'er is probably off air till a solution is found :(

Just wondering is there any company like sipka etc who does repair etc and if yes, will it be worth getting this set repaired if it can be??
When All Else Fails !!
Last Edit: 9 years 2 months ago by Simple Ham'er AP2CJ.
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