O.T. Icom IC27A 2 meter mobile rig fixup (Resolved!)

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Kenn
Posts: 51
Joined: Fri Apr 08, 2016 8:43 pm

O.T. Icom IC27A 2 meter mobile rig fixup (Resolved!)

Post by Kenn » Sat May 20, 2017 5:36 am

Greetings all,

Totally off topic, other than that I'm using an RTL-SDR on the test bench ... so I have an Icom IC-27A 2 meter mobile radio I'm fixing up. A few questions:

Mainly, the original PL type antenna connector was in bad shape. I replaced it with a right-angle BNC, soldering the braid to the outer connection. I crimped & soldered a loop to the inner conductor. It's a radio shack 278-0126.

Image

My concern is, this type of connector allows for a small gap where the outer shielding does not completely surround the inner conductor. Is this likely to cause issues?

The radio is outputting 5 watts on low (as it should) and ~15 watts on high (it should be 25). Someone suggested that connector could be causing the transmitter to dial back it's output. Your thoughts?

As I'm not yet proficient at soldering PL-259 connectors and there's only a few inches left on the back of this radio, does anyone have some recommends for crimp-ons that are good?

Thanks!

-Kenn
Last edited by Kenn on Mon May 22, 2017 4:07 am, edited 2 times in total.

snn47
Posts: 153
Joined: Tue Dec 27, 2016 11:00 pm

Re: O.T. Icom IC27A 2 meter mobile rig fixup and BNC connect

Post by snn47 » Sun May 21, 2017 7:36 am

If you have accesss to a Standing Wave Ratio meter use a 1/2 wave coax to meassure the reflections. Both cable and SWR have to have the same impedance as your TRx output connector.

You did not show a picture of the gap you ask about. Do you refer to a PL-type antenna connector (PL-259 also called UHF or Unuseable for High Frequencies because it is a shielded banana cable with out that the impedance matches the cables impedance), but show a BNC male connector.
Is your question for a PL259 or the BNC male connector?
Does this
for a small gap where the outer shielding does not completely surround the inner conductor
relate to the connector or where you connected it yourself?
Finally your Radio Shack number does not lead to a connector.

Kenn
Posts: 51
Joined: Fri Apr 08, 2016 8:43 pm

Re: O.T. Icom IC27A 2 meter mobile rig fixup and BNC connect

Post by Kenn » Mon May 22, 2017 4:06 am

Over on eham.net, K5LXP suggested I check voltage drop on the power cable. That appears to have been the issue.

I checked the voltage at the radio's main-board during transmit and on high power it was dropping to 11 volts. Voltage at the power supply terminals is always a constant 14.0.

I replaced cig lighter plug that the radio came with in favor of crimped & soldered loops, deoxit the fuse connections, and soldered all power lead crimp connections.

While I was at it, I cleaned all antenna plugs & jacks on my patch cables and meters. I haven't used them in some time so there was considerable dirt on the swabs.

The radio now outputs low to mid 20's and current draw is ~5.5 amps. Voltage at the main-board is now 13.5. I can live with this.

I think I will make it S.O.P. to solder all crimped connectors and avoid cig lighter plugs for anything more than a cell phone charger, even if all the above appears to be solid.


-Kenn

snn47
Posts: 153
Joined: Tue Dec 27, 2016 11:00 pm

Re: O.T. Icom IC27A 2 meter mobile rig fixup (Resolved!)

Post by snn47 » Mon May 22, 2017 11:53 pm

Congratulationfor solving your problem, however I am surprised that you have no voltage drop during transmitt.

Personally I do not crimp any connector used for transmitt purposes nor use any form that jist presses connections with higher current.

There are lighter plug that that allow to tighten the cable with a screw like in AC connector.

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