Running multiple Radios off a single longwire antenna?

[startreksteve]

Hi Guys,
I run several radios (Realistic DX-394, Yaesu FRG-7, Yaesu frg-7700, Kenwood R1000 and a Tecsun PL880) all with a wire running from each particular radio with the other end crocodile clipped to the DX-394's Whip antenna. Its now got seven crocodile clips on it and its starting to look a bit untidy! Im wanting to have some kind of block with all the wire going into it and the longwire antenna going into that. My son suggested an earth block which would have done the job, but it seems only suitable for thick house mains earth wire, I don't think I would be able to tighten it onto my thin longwire antenna. Any ideas for a cheap solution? I don't know what to search for in google word-wise.

Thanks

Steve

[Station X]

Chocolate block? Common the connections on one side, connect the receivers to the other.

[G6Tanuki]

Choc blocks are worth a thought yes. If you fasten the wire into one screw only and remove the other screw you can plug a 4mm banana plug into the hole.

Personally I wouldn't have all the radios connected to the antenna at the same time though.

[Herald1360]

Originally Posted by G6Tanuki

Choc blocks are worth a thought yes. If you fasten the wire into one screw only and remove the other screw you can plug a 4mm banana plug into the hole.

........

Only if the choc bloc is just the right size. Too small and it won't, too large and you'll need the screw to use the plug as a ferrule.

[Glowing Bits!]

The way I did things was rather crude at best, it involves a long length of speaker wire with choc-block tap off points where the radios are, assuming it has no in-built antenna, the other end is croc-clipped to the overhead cantenary wire across the garden, it holds up the phone line/ethernet/Xmas ropelight.
Pic below is the connection to the outdoor bit, crude but works.

[stuarth]

Choc block connectors are not ideal for connecting several wires together. A better solution would be a Wago block. A multi way chock-block is multiple separate electrical connections. A multi way Wago block connects all the wires going to it (up to 8) together.

Wago blocks are available to join from 2 to 8 wires, and come in two basic types, lever and push in. Push in types are intended for permanent electrical installations with solid wires (they make wiring a ceiling rose a doddle!), what’s needed here is a lever type.

I’ve used the term ”Wago”, I think they were the originators of the design, but there are now lots of very similar connectors available, some even replicate the Wago colours. Other manufacturers make lever connectors which are double ended, and a multi way double ended block is several separate electrical connections just like a chock block,so not what’s needed here.

[startreksteve]

Originally Posted by G6Tanuki

Choc blocks are worth a thought yes. If you fasten the wire into one screw only and remove the other screw you can plug a 4mm banana plug into the hole.

Personally I wouldn't have all the radios connected to the antenna at the same time though.

Why? Lightning?

Steve

[majoconz]

Personally I wouldn't have all the radios connected to the antenna at the same time though.

Why?

Simply....When a radio is tuned to a station, the tuned circuit at the aerial terminal is a high impedance at that frequency to 'select' that station. All other signal frequencies in that band are sucked down to ground via the now low impedance of the antenna coil/capacitor. Parallel up a few radios to one aerial and you will probably hear...nothing!

You need what is commonly called a multicoupler or antenna distribution amplifier - not cheap. I run five VLF/HF receivers through a "Reaction Instruments 409-2 multicoupler" that I bought on our local auction site cheaply and it works really well.

https://blackradios.terryo.org/docum...r-brochure.pdf

[G6Tanuki]

Yes, there are several issues with connecting multiple radios in parallel to one antenna.

Firstly - each radio acts as a 'load' on the received signal - if you have N radios connected in parallel then in the best case each radio will see 1/N of the received signal. In the worst case you can get 'suck-out' where the antenna tuned-circuit of one radio acts like an absorption-wavemeter and preferentially gobbles-up signals on the frequency it is tuned to. This can make "trying to hear the same station on two radios" a bit of a fool's errand.

My other concern is - if one of the radios sharing your longwire is an AC/DC type with a live-chassis - and the isolating capacitor in the antenna circuit goes short-circuit then - even when said radio is switched-off - it can be essentially connecting your antenna to mains-live. Any other radio connected to the antenna - even if not actually plugged-into the mains - could be raised to mains-potential, resulting in the risk of a nasty 'bite' and/or damage to its front-end circuitry.

Then there's the addidional issue of local-oscillator-leakage if trying to use two radios at the same time fed by a dingle antenna without adequate isolation. The WWII-era HRO was well-known for radiating the third-harmonic of its local-oscillator back up its antenna, to the extent where a with receiver operating on 14MHz the harmonic could block-out reception of Band-I TV signals!

[startreksteve]

Originally Posted by G6Tanuki

Yes, there are several issues with connecting multiple radios in parallel to one antenna.

Firstly - each radio acts as a 'load' on the received signal - if you have N radios connected in parallel then in the best case each radio will see 1/N of the received signal. In the worst case you can get 'suck-out' where the antenna tuned-circuit of one radio acts like an absorption-wavemeter and preferentially gobbles-up signals on the frequency it is tuned to. This can make "trying to hear the same station on two radios" a bit of a fool's errand.

Hmm there doesn't seem to be a problem with reception at all..

Steve

[G6Tanuki]

I guess you're not digging-down to get that last-microvolt of signal from a DX station in the Falklands or Antarctica....

For a suitable local station compromise (all engineering is a compromise) just put a 1000 ohms or so in series with each set. You will get a slightly smaller signal but much less interaction twixt. All can be used then.

[startreksteve]

Originally Posted by G6Tanuki

I guess you're not digging-down to get that last-microvolt of signal from a DX station in the Falklands or Antarctica....

I've been trying to get LRA36 for twenty years!! no joy yet!!