Touching coax cable connection

[Limeybastard]

Fixed mounting and bonding, yeah definitely. Hinges on trunks and hoods are OK for DC conductivity but poor for RF so bonding straps across those to bond the hood/trunk to the main body make a significant difference. Try it yourself even if you're using a magmount. Get your SWR meter out. Check what channel it starts to rise and hits a certain point, say 1.3:1, note that down then go the other way and do the same. Do some bonding, just even one strap across the hinge of the hood to the body. Do the test again and you should find that the SWR point you were measuring now occurs on lower channels. That's because the resonant frequency of the antenna is dropping as the RF ground improves. If you were to use a 102" quarter wave whip without any matching coils and an antenna analyser you'd see the frequency of the resonant point where x=0 had dropped and also that the value of R comes nearer to the perfect 36.8 Ohms.

You know in another subject when you mentioned looping / turning the coax 9' from the magmount for mounting it on for example a chimney top with a 3x3' metal base. To prevent RFI. So for clarification purposes, the loop is 9' away from the base of the magmount right? If so, any particular distance to leave the looped up cables, away from ground plane?

 

[redbeast]

Cheers for your kind explanation, appreciate it. All the above was jn receive mode and touching the case didnt change anything, just touching the pl259 connection.

The coax is a Wilson 1000 mag, fixed ( length)coax.

LB......just had a similar problem with my cobra 25 ltd. I run a sirio 2000 on a mag mount. Tried swapping antennas, mics, finally looked at the inside of the radio. What I found was a resistor soldered to the center coax wire. At first i thought it shouldnt be touching, so i bent it away- no tx or rx. Soldered it back in place to center wire and life is good. Had had thiss issue for a while, but intermittent, finally noticed that pulling down on pl259 got my dx back! Bad solder joint from vibration. Maybe this will help. 73

 

[Limeybastard]

LB......just had a similar problem with my cobra 25 ltd. I run a sirio 2000 on a mag mount. Tried swapping antennas, mics, finally looked at the inside of the radio. What I found was a resistor soldered to the center coax wire. At first i thought it shouldnt be touching, so i bent it away- no tx or rx. Soldered it back in place to center wire and life is good. Had had thiss issue for a while, but intermittent, finally noticed that pulling down on pl259 got my dx back! Bad solder joint from vibration. Maybe this will help. 73

My hunch was that I hadn't connected the FME type connection properly where it connects to the radio coax cable. The other thing I noticed was the jumper lead , one side doesn't grip via the teeth well.

 

[M0GVZ]

You know in another subject when you mentioned looping / turning the coax 9' from the magmount for mounting it on for example a chimney top with a 3x3' metal base. To prevent RFI. So for clarification purposes, the loop is 9' away from the base of the magmount right? If so, any particular distance to leave the looped up cables, away from ground plane?

If you're wanting to use the coax for a ground plane then yes it needs to be 9ft away from the base of the mag mount. You don't want the looped up cables on the groundplane at all because that then just potentially puts RF back on the coax after the choke so it gets to your radio. If they have to be try to space them away from being in direct contact.

 

[Limeybastard]

If you're wanting to use the coax for a ground plane then yes it needs to be 9ft away from the base of the mag mount. You don't want the looped up cables on the groundplane at all because that then just potentially puts RF back on the coax after the choke so it gets to your radio. If they have to be try to space them away from being in direct contact.

So the looping of the coax is or is not in addition to me placing down a 3x3' metal ground plane?

Basically, do I still need a counterpoise for the magmount if i utilize the looping of coax? Mucho gracias ;-)

 

[M0GVZ]

In addition. 3' x 3' isn't really long enough for 11m so by using 9ft of the outside of the coax braid as a counterpoise by doing the coil 9ft from the mount then you're going to improve the efficiency and if the coax is hanging down from the chimney the antenna will function quite like a vertical dipole with the 9ft of coax between the mag mount and the coil being the bottom leg.