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Kenwood & EF Johnson Forum - For discussion of land mobile radio products manufactured by Kenwood or EF Johnson. For discussion of Kenwood Amateur Radio Equipment, please use the Amateur Radio Equipment forum.

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  #21 (permalink)  
Old 02-02-2018, 1:21 AM
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There is little in the meter itself to give you issues. It's the line section, a short cable and a meter. The more important parts are in the slugs. Those can be checked fairly easily.
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  #22 (permalink)  
Old 02-02-2018, 12:02 PM
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The different connectors is an old technician trick. Simply make up a jumper cable with an N on one end and a UHF on the other and you don't need any adapters.

Point the arrow on the slug in the direction you want to measure power (forward or reflected). SWR can be found from a formula but there are graphic charts that show the SWR calculated from the forward and reflected power. It is easy to laminate the chart and paste it on the back of the meter for reference.
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  #23 (permalink)  
Old 02-02-2018, 12:46 PM
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Where on the west coast is the OP located? I have several Bird 43s and slugs to compare if he wants to see if his are accurate.
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  #24 (permalink)  
Old 02-02-2018, 2:55 PM
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Quote:
Originally Posted by prcguy View Post
Where on the west coast is the OP located? I have several Bird 43s and slugs to compare if he wants to see if his are accurate.
prcguy
I appreciate the offer,

I'm up in Canada around Vancouver BC

Thanks,
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  #25 (permalink)  
Old 02-02-2018, 3:01 PM
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Quote:
Originally Posted by WA0CBW View Post
The different connectors is an old technician trick. Simply make up a jumper cable with an N on one end and a UHF on the other and you don't need any adapters.

Point the arrow on the slug in the direction you want to measure power (forward or reflected). SWR can be found from a formula but there are graphic charts that show the SWR calculated from the forward and reflected power. It is easy to laminate the chart and paste it on the back of the meter for reference.
BB
That's all I was planning on doing. I need to make up a short jumper for radio to meter anyway. Doesn't matter if I buy a UHF or N connector they are roughly the same price.
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Old 02-02-2018, 3:22 PM
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I'm a bit too far for a casual drive.
prcguy

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I appreciate the offer,

I'm up in Canada around Vancouver BC

Thanks,
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  #27 (permalink)  
Old 02-02-2018, 3:59 PM
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I'm a bit too far for a casual drive.
prcguy
Bummer, but I still appreciate the offer though!
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  #28 (permalink)  
Old 02-06-2018, 9:29 PM
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Well............

Acquired a male N connector today.

Eager to check out the Bird meter, I hooked up to the tk-7360V through to a dummy load. Nothing, barely any deflection of the needle.

Bummer....

poke, prod, twist, turn Eureka!
D'oh!! gone again... Wait, what??


I twist the connector in to the back of the radio, key up the mic, nothing.... Gently tap the antenna connector on the back of the radio. I can hear the scratch on another receiving radio until the needle jumps to 54watts transmit power, wiggle it around and the needle drops out again.

Ok, the TK-7360V has some sort of cold solder joint in the antenna output....
edit: or the antenna connector is bad.

The TK-7360H is only putting out ~38watts transmit power. That'll, make my head spin...
My old ancient TK-760H is putting out 52 watts.

Ok, ok... I have no idea if the readings out of the meter are right, the meter has helped me confirm one suspicion and identify another problem I had no idea about...

Not bad...
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  #29 (permalink)  
Old 02-06-2018, 9:39 PM
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Now I KNOW I have a cold solder joint!

Pulled out the screws and out it popped...
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  #30 (permalink)  
Old 02-06-2018, 9:45 PM
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As they say "Well, there's your problem right there!"

Heavy coax connected directly to the radio will do that. Same thing happens on Motorola's with the mini-UHF connectors when someone tries to connect LMR-400 directly to it, or a big stack of adapters.

Easy fix. Reinstall, reflow the solder. maybe add a bit more if necessary.

As for the radio outputs being different…
Unless they were purchased new by you, I wouldn't worry. Not uncommon for them to get turned down a bit. Could be a number of causes. Just resist the urge to go into the service software and crank it up without following the full procedure.
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  #31 (permalink)  
Old 02-06-2018, 10:01 PM
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Actually, it was defective from the factory.
There was flux stuck to the antenna connector and that's it. The metal on the antenna connector never got hot enough for the solder to stick to it.

My thumb nail and a little bit of scraping made it look brand new and unused.
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  #32 (permalink)  
Old 02-06-2018, 10:05 PM
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Originally Posted by westcoaster View Post
Actually, it was defective from the factory.
There was flux stuck to the antenna connector and that's it. The metal on the antenna connector never got hot enough for the solder to stick to it.

My thumb nail and a little bit of scraping made it look brand new and unused.
Good catch. Really rewarding when you can fix stuff like that on your own.
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  #33 (permalink)  
Old 02-06-2018, 10:21 PM
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Ok, full circle with a conclusion to my receive sensitivity issue.


The culprit in this case was a cold solder joint on the antenna output.

I first tinned the antenna connector before reinstalling in the radio. Once in, there was a small wire on the PC board that was bent back into place with a gob of solder run the full length.

Now it receives every bit as good as the other radio.


Done.


edit: Now I know why I found the radio in the pawn shop for little money. Buddy got fed up with the thing.
I think the Bird was worth the money. While I suspected it was something like this, I had no way to truly identify the issue.
It certainly stood out as a problem once I hooked up the meter....

Last edited by westcoaster; 02-06-2018 at 10:26 PM..
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  #34 (permalink)  
Old 02-07-2018, 12:09 AM
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Quote:
Originally Posted by westcoaster View Post
Kenwood TK-7180H 0.25μV (wide) 0.28μV (narrow)
Kenwood TK-7360H 0.28μV (wide) 0.35μV (narrow)
Kenwood TK-760HG 0.25μV (wide) 0.33μV (narrow)


Am I correct in thinking with the above three radios the TK-7360 will not perform as well as the other two when it comes to picking up distant signals?

How big a difference will 0.03μV make?

In playing around with a TK-7180H and a TK-7360H last night, I noticed enough of a difference with my radio's to make me go check. But how much is individual radio tuning and how much is radio specification?


Thanks,
The difference is not significant. There are other specifications that the radio must meet and those are:

Receiver adjacent channel selectivity, - the ability of the receiver to operate to its maximum sensitivity performance when another station is on an adjacent channel.

Intermodulation (IM) rejection, - the receiver having sufficient dynamic range and ability for the receiver to reject interference potentially caused by strong signals overloading it.

Spurious response rejection, - the ability for a receiver to reject certain signals and noise energy outside of its bandwidth.

All of these are "real world" situations that would reduce its effective sensitivity.

If you compare the three receivers you might find that the one with the worst terminal sensitivity actually outperforms in those areas listed.

The terminal sensitivity on the spec sheet is measured on a work bench, with a signal generator and SINAD meter inside a Faraday cage shield.

Where the radio must perform is out on the street among 100's of other transmitters in band, out of band, broadcast and electrical noise. I once discovered a low band repeater that had terrible desense because the manufacturer did not feel it necessary to test or meet the spurious response specification below the operating frequency. There was no apparent on channel noise from the transmitter through the duplexer, yet the repeater did not work. There was however noise from the power amplifier at about 15 MHz that raised the receiver's internal noise floor.

Industry document TIA/EIA-603 required testing that receiver at those frequencies. Had the manufacturer bothered to test, they would have used a proper bandpass filter in the receiver.

Today a ham showed me his $35 Baofeng radio in response to my showing him a 1998 vintage Motorola Systems Saber (that cost $2,900 in 1998 money). I bit my tongue.

A radio with terrific sensitivity and poor filtering will work fine in very rural areas, but when you bring them into an urban environment they will misbehave.

I might add, when I worked in the lab at Motorola , we had a VHF radio model with three tiers of performance. There were very different receiver designs across the tiers. The cheap radio had a simple receiver with coils and ferrite tuning slugs, the expensive one had a preselector filter with helical coils and brass tuning screws. Then we had a high power radio in the lower tier. It was exactly the same radio as the high power upper tier radio. The heatsink was painted white on the cheap one and black on the pricey one. Other than that, exact same parts list.But the specifications were very different, the cheap radio had specs mirroring its crappy low tier siblings. I asked the product manager "what gives". He said, "its specsmanship!" "We would never sell the high tier model if the low tier one had the same published specs". So I learned marketing in one quick lesson!

That's the rest of the story!
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Last edited by RFI-EMI-GUY; 02-07-2018 at 12:25 AM..
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  #35 (permalink)  
Old 02-07-2018, 2:01 PM
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There IS way more to receiver performance than just sensitivity.

RFI-EMI-GUY nailed it.
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