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Cando, what radio did you get? Are you going to join VKS737 or similar radio networks? (It obviously needs their frequencies fitted).

If so, you can get a tapped whip antenna covering all their frequencies for around $250 (eg Bushcomm Bushranger). Sometimes they appear on ebay or you can make a cheaper simpler one from a 9m fibreglass fishing pole and 9m of wire wrapped around it. This is centred around 8mhz but works reasonably well from 5 to 10mhz. I have both types.

We are on the road near Yulara at present and will be out of network range for a couple of weeks in the deserts of WA or we could talk more on the subject.

First you need to organise what frequencies in the HF you have and what you want. When you have the correct HF frequencies fitted then go to Bushcomm and you can either get a custom HF antenna to suit or a General HF Antenna off the shelf like the 13 tap VKS unit. Many tap antennas out there were custom built to suit the radio, so second hand is not a good idea unless it matches the radio frequencies you have in the HF.
I would recommend fitting VKS-737 frequencies and using their service.

The Bushcomm @ $245 seems incredible value.

I have a Barrett auto tune antenna which is a bit delicate and i don't trust it. I need a new whip for it which is just a piece of stainless rod and that is $132, it seems expensive compared to a wound multi-tap.

I think I will be going with Bushcomm, thanks guys.

Peter you can use any 27mhz CB whip antenna on top of the Barrett autotune antenna.

You can even use a length of wire about 2m long with great success. I used to install HF's in vehicles and on exploration type vehicles that were used in thick scrub we would have two insulated posts on opposite corners of the roof rack and just run a length of wire between them connected to the autotune antenna and they would quite often give better signal than a vertical whip.

The Barrett antennas are pretty tough, much tougher than a Codan one.

Just for the record, on a vehicle, a quarter wavelength vertical antenna will always provide better performance than a tapped whip or auto tune antenna (both of which are compromises to achieve small size).

It can be any wire supported or raised in the air, either by a fibreglass rod or a non-conductive rope to a tree/building. The angle is not critical and it can also be laid along the ground in the direction of required communication and is therefore a useful emergency antenna.

To calculate a 1/4 wavelength antenna, 75/Freq in Mhz = length in metres. So at 8.022 MHz (VKS ch2), 1/4 wavelength is 9.35m but the length isn't critical.

However erecting a 1/4 wavelength antenna can be a handful, especially around power lines, see this article, and can't safely be used while moving.

But whatever primary antenna you use, also pack 9m of wire for use if it gets broken.

"But whatever primary antenna you use, also pack 9m of wire for use if it gets broken."

+1 Excellent advice!!  Exactly what I do as well.  I have a Q-Mac with an auto tune but always carry a throw wire antenna as well.  

Yes agree totally we would often demonstrate to a customer how they could use a length of wire instead of the autotune if it got broken etc and the much better reception amazed them.

Hey Guys

Could you please explain (exactly) how the connection is made between the piece of wire and the coax connection on the radio. Can I just steal some wire off my neighbors fence to do this or are we talking some special wire. Does it need some insulators? or insulated wire?

Peter I carry a piece of green insulated 240v earth wire of about 12 m length with a coax connector on one end to connect to the radio.  It has a few joins in it to get the right length for different frequencies. Somewhere I've got a chart that gives the length required for each frequency, it or the formula to work it out is on the VKS website.

You will also need a similar length of wire to lay out along the ground which is connected to the coax plug on the shielding (outer).

I've also got a shorter length of wire about 1.5 -2m long with a loop on one end to connect to the top of the autotune antenna which isjust tied to a tree using rope or some other non conductive item.

sounds great, but I'm a bit confused, please confirm if I have this right..

crystals in my old antique Codan cover RFDS bases and VKS ch 1 and 2
so I should have 2 wires of the same length coming together at the radio coax connection, the elevated wire connected to the centre pin on the coax and a separate ground wire of the same length connected to the sheild

both the elevated and ground wires should be adjustable to 1/4 wavelengths..
=75/freq in Mhz e.g =
75/8.022 MHz = 9.35m for VKS ch2
75/5.455 MHz = 13.75 for VKS ch1
similar lengths for RFDS bases 75/5.11, 5.145, 5.3, 5.36 and 5.41

Rick #149

This is all great information. I have been wondering how to deal with antennae - I have a Qmac and an old Codan "Lunch box" . Haven't decided which to use in the Oka yet.

I would be grateful for some expert advice.

In my youth, I used a pi-coupler circuit to match random wire antennae to valve finals, and they worked wonderfully well but I recall lots of arcing across the tuning capacitor plates on loud passages. This didn't worry the valves, but I have real concerns that I could easily blow the transistor output devices if I got the antenna tuning wrong. Is this why the pi-coupler doesn't seem to get used any more?

How does one safely tune a random wire to a solid state output transmitter?

Grateful for any thoughts,

Cheers,

Paul

Not sure where you live but this Melbourne Ham radio group can make up a whip with the VKS737 frequency tappings on it  Famparc hf antenna

From memory the price was less than $150

Paul, all modern radios (since at least the 1970's, including your Codan Lunchbox) include built-in protection against faulty or mismatched antennas.

If the antenna is wrongly matched, you'll notice that the Transmit light (or similar) will shine less brightly when you talk and the signal won't get though as well. That's the protect system working to reduce the power output to protect the transmitter circuit, especially the power transistors.

Antenna matching is not normally a problem with emergency HF radios since they work at fixed frequencies (eg VKS737) and into matched antennas (a tapped whip or an auto tune which matches itself to the frequency being used).

So unless the protection system fails (eg a lightning strike on the antenna), you are probably OK with any antenna length (although performance will suffer) but it's not good practice to deliberately mis-match a transmitter system.

In my case I use either a tapped whip for normal service, or for better performance, a 9m vertical antenna which is a perfect match to VKS channel 2 (8022khz) but also works quite well on channel 1 (5455khz).