21/08/2025
CODAN 9350 AUTOTUNE ANTENNA:
This article was originally written by Peter Harland, a good friend of this Network and of David Collins from HF Radio in Queensland. Sadly we lost Peter some years ago when ill-health took him. Given that we regularly hear Subscribers with Codan 9350 Antennas not tuning when they call, it's prudent to reproduce this article as a reminder to take care of your 9350 autotuner.
Peter was very clever with his hands and also came up with a nifty idea to modify a 6 foot long 27 MHz CB whip.
Enjoy.......
Hints and Precautionary Steps for the Codan 9350 Autotuner.
The 9350 is a rugged unit and, with a few simple tips, its trouble free service life can be extended. One of the main problems, in later life for the tuner, is not tuning and “beeping” because of wear on the tuning coil and step motor contact points caused from vibration, and by leaving it permanently on 8022 kHz (Channel TWO).
When transmitting, if the radio beeps to indicate that the antenna tuning has failed, the radio will only put out 10 watts of power, not its rated 100 watts.
When travelling, vibration from corrugated, rough roads can be harmful to the antenna. When not using the radio, you should set the Autotuner on the lowest frequency you can find, say a 2 Meg RFDS frequency or VKS Channel 5. Hit tune then turn the radio off. The lower down the coil that the step motor is parked, the less vibration will hammer the antenna.
It's vitally important to exercise the autotuner. Do this when you're parked. Select a high frequency, say VKS Channel 4 or a 27 MHz CB channel, tune it and then select a low frequency (RFDS 2 Meg or VKS Channel 5 - 3995 kHz) and hit tune again. Do this a few times, up and down, hitting the TUNE button after each frequency change. Park the Codan 9350 on the low frequency again when finished. This is particularly important if you're parking the vehicle away after a trip and not using the radio for a while.
The reason for exercising the Codan 9350 Autotune is because it is an electro-mechanical unit. A fine coating of special grease is put on the inside of the coil to aid tuning contact and to reduce friction. After time, the grease hardens and impedes the effectiveness of the step motor from tuning correctly. Exercising the step motor regularly stops the grease from hardening and lubricates the tuning coil and step motor contact point.
It costs a lot to replace the tuning coil and have the unit serviced by an authorised dealer so this method is worth the time you spend, exercising the autotuner.
A Modified 27MHz CB Whip:
Another problem, particularly with early model tuners, was that the top of the plastic casing, where the spring base screws could crack over time because of the weight of the original stainless steel antenna and spring. Once again this is caused by vibration. I replaced my antenna with a home made lighter version. I made an adaptor for the top of the autotuner to attach a CB spring and an 1800mm long CB helically wound Antenna.
Adaptor: If you're cleaver enough with steel, you can make an adaptor so the CB antenna and spring will attach to the autotuner. Cut an 18mm diameter steel, or brass rod, to a length of 50mm. Drill one end to 45mm depth and tap with an M14x2 thread to suit the thread on top of the 9350. The other end of your adaptor is tapped and fitted with a 20mm long 5/16” UNF bolt with 27 tpi (turns per inch), modified to fit inside the end of the adaptor. If you have a mate with access to a lathe, use him.
Spring: A spring can be purchased from Jaycar or any UHF/CB Supplier. The spring will have a 5/16” 27 tpi thread top and bottom. If you have to use a 26 tpi bolt you will need to re-tap the CB spring base to suit.
Antenna: Find an 1800mm, 27 MHz CB whip. As it is, the whip has too much wire wound into it and needs to be modified. On 27MHz Citizens Band, the antenna is a top loaded type and the top loading coiled wire can be removed. This brings the antenna into Codan 9350 tuning range of 2-30MHz.
To modify, remove the plastic tip from the top and cut the fibreglass about 2 cm above the coil. Don’t cut the wire. Use the cut piece of fibreglass to gently pull the wire from the top loading, outwards. Approximately 8 metres of wire will be removed. The wire comes out easily. Pull until restriction is felt and cut the wire level with the top of the whip. Use a heat gun to shrink the plastic back onto the whip and replace the plastic tip.
This modification will give you the same performance as a Codan stainless steel or fibreglass whip. It should tune from 2050 kHz to 30 MHz. The modified whip weighs way less than the original stainless steel whip. I have used this modification on my vehicle for the past 10 years with no problems. There is not much deflection of the whip antenna at 100kph and it's strong enough to attach a safety flag.
