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INTERMITTENT RECEIVE

Stellasarat

Active Member
Sep 17, 2013
213
49
38
The last couple of weeks I've noticed the receive on my Uniden Madison acting peculiar. It's fine for one moment then it makes a kind of swishing sound as the needle on the meter drops down around 2 s units and as a result the receive gets quiet. I noticed this happens when it's windy outside. Although it's not windy today it has been raining. I thought it might have been the pl 259 on the antenna. I checked it and everything is tight. I thought it might have been the Madison itself but, i used the antenna switch to switch over to my Sonar which I use for am use. Same exact issue on the sonars receive After shutting the Madison off for a while then turning it back on I notice they receive is quite low until I key the microphone for the first time. I do use the Madison with an amplifier. The amp is a DNA Phantom. When I key the microphone for the first time I hear a relay click and then the receive comes back up. This doesn't solve the problem of my receiver jumping up and down as, it might be a different issue. After the first key down the relay I'm assuming opens and the receive comes back up. As I mentioned I think this is a different issue but, might be related to receive dropping up and down every few seconds. My antenna is an IMAX 2000 wit an MFJ 915 rf choke. I checked the pl 259's on the 915 and they were tight. I'm pretty sure one of you probably is familiar with this issue and might be able to point me in the right direction. Thank you.
 

space cowboy

Quack Quack
Oct 16, 2012
1,369
449
93
Michigan
is this happening with signals or just noise?

sounds like a bad connection somewhere. re-solder the pl259 connector, check the coax with a multimeter for internal breaks. I'm not familiar with the antenna, but if it assembles, check all those connections too.
 
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Stellasarat

Active Member
Sep 17, 2013
213
49
38
is this happening with signals or just noise?

sounds like a bad connection somewhere. re-solder the pl259 connector, check the coax with a multimeter for internal breaks. I'm not familiar with the antenna, but if it assembles, check all those connections too.[/QU. Signals also.
Signals also drop then jump back up to where they should be. This happens ever few seconds in adverse weather.
 

Stellasarat

Active Member
Sep 17, 2013
213
49
38
Sounds like a bad coax connector at the antenna - maybe?
Between the choke and antenna I went with a double ended conetor (no coax) so I'm gonna replace the pl 259 at the coax antenna connection. The coax is lmr 400. Not the ultra flex. The coax is quite heavy and, maybe the heavy wind and weight of the coax itself looosened the 259. That would explain the ether high winds or just the rain setting this recive problem off. I failed to mention no Change is noted in swr when the recive acts up. Thank you.
 

M0GVZ

Sr. Member
Oct 18, 2011
1,729
1,465
173
I had this happen with a compression fit PL259 I used on some Westflex 103 coax which like LMR400 is very heavy. What happened is over time the 40 odd feet of coax dangling below started to pull the coax out of the PL259 and eventually it did like yours due to an intermittent contact with the braid. I would find that when it started acting up that if I briefly keyed the radio it went good again for a couple of minutes.
 

Stellasarat

Active Member
Sep 17, 2013
213
49
38
I had this happen with a compression fit PL259 I used on some Westflex 103 coax which like LMR400 is very heavy. What happened is over time the 40 odd feet of coax dangling below started to pull the coax out of the PL259 and eventually it did like yours due to an intermittent contact with the braid. I would find that when it started acting up that if I briefly keyed the radio it went good again for a couple of minutes.
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It wasn't the pl 259 at the end of my LMR 400. The double male connector that attaches my mfjj 915 RF choke to the antenna was one turn loose. I'm assuming that one turn left the center pin not making good contact with the antennas PL 239. I think it was like that for quite a while because the difference between my receive over the last few months and after the connector was tightened is night and day. It's a pleasure 2 listen. I'm purchasing a bhi DSP speaker and hoping that my listening experience will be that much enjoyable. Thanks to all who responded. 73
 

BBB

Well-Known Member
Jan 17, 2012
744
402
73
All coax connections must past the "Wiggle Test"

Its as simple as it sounds, but even I get bit by a bad coax jumper from time to time that doesn't show on the SWR meter due to the intermittent nature of the failure.

Coax "Wiggle Test" :

Step 1: On a regularly scheduled basis and while radio equipment is in receive mode, aggressively wiggle and tug at the coax cable near all coax connectors with about 5 lbs of force. If any, and I mean ANY difference in signal is heard or observed, check for correct tightness of coax connector. If connector is tight, suspect connection inside PL connector is bad/intermittent or PL jack has issue in the equipment, such as loose grounding screws/ rivets or the center conductor lead or pin is loose.

Step 2: Do not transmit with equipment until corrective actions have been taken to remedy the loose or failed coax connections and all connections then pass the coax "Wiggle Test" and VSWR is within proper limits.
 

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  • @ ButtFuzz:
    on the connector with the green wire, if you short that to a nearby black wire, the power supply will turn on. (for use as a bench supply or whatever)
  • @ ButtFuzz:
    And IIRC, the purple wire is -12VDC, but that is from memory and it does not serve.
  • @ ButtFuzz:
    So if you need, say, 7v, connect + to the Yellow wire and - to the Red wire.
  • @ ButtFuzz:
    or or you need 9v connect + to the yellow wire and - to the orange wire. note: not all PSU's have the orange wire nowadays, as many manufactures had the voltage regulation on the motherboard, and all the power supply gives is 12 vdc
  • @ BJ radionut:
    Thanks ROB will check it out!~!! got to clean the work bench a little make room for that big case :)