First steps in SW and AM radio on board, with a Lowe HF150.

[sarabande]

From the previous boat, I have a Lowe HF150 which seems to have a good reputation.

Receiver only, but I am happy at this stage with that.

For the boat I understand that I will need a whip aerial. Can some clever electronics person advise on the length of aerial suitable for general radio work, and more particularly for weather data (gribs, etc) please ?

Also, I believe that aerial wire (coax and fittings ) are very important, so advice on that as well will be welcomed.

TIA

 

[Martin_J]

Hi.. Looks like are a few places on the web that have the manual to download.

Looks like you should use a 4:1 or 9:1 unun (unbalanced co-ax / unbalanced long wire) and then attach the wire.

The unun (sometimes called Balun meaning balanced to unbalanced!) can be seen here..
https://m0ukd.com/homebrew/baluns-and-ununs/91-magnetic-longwire-balun-unun/.

To make they're quite easy but the ferrite cores are relatively dear if you only want to buy one due to postage. Search online and the made up unun is easy to find on ebay. They convert from the co-ax connector and allow a 'long wire' to be attached.

Wire length - Whatever you have although something like the length of the average cruising boat SSB backstay antenna would work.

There's a nice article here about the Lowe HF150 and how to build a multi-band antenna for your garden.. It'll resonate on each band nicely...

http://www.mds975.co.uk Six band sagger antenna

As to antenna wire. I usually use the Nevada military style kevlar antenna wire..

http://www.nevadaradio.co.uk/antenna-accessories/antenna-wire/

Nicely robust and quite disguised in the countryside..

 

[GHA]

For the boat I understand that I will need a whip aerial.

For receive the antenna is much less important than for transmit, try a length of wire up the rigging and see what you get - I've had surprisingly good wfax images before across Biscay with a little degen 1103 just resting the antenna against a chainplate down below in a wooden boat. And before knowing anything about radios had wfax all the way back from the Carib using an FM radio antenna at the top of the mast. Completely wrong antenna but images were fine all the way back.

You won't get gribs with a reciever, just weatherfax - which is plenty useful on it's own.

 

[MM5AHO]

+1 for just trying a wire first. You could end up putting all manner of matching into the system (balun, un-un etc) with no discernible effect. You can easily add refinements later if needed.

 

[GHA]

Also you can check what other people are receiving here >

http://www.websdr.org/

 

[William_H]

As said try just a wire into the coax connector on the radio. Hopefully the ground of the coax will be connected to the negative of the boat and so to the sea. Try a connection if not. An antenna (long wire or whip) presents an apparent impedance which varies with frequency. Apparent impedance is that which requires an impedance at the receiver that matches the antenna impedance for max power transfer. Your radio with a 50 ohm coax connector presumably would suck the most power out of a 50 ohm antenna. A 33 ft long wire at about 7mhz gives a resonance which gives 50 ohms. At shorter wire the impedance rises as it does at higher and lower frequencies. (as you move away from resonance) (16.5 ft for 14mhz) The Unun in the link is designed to match the higher impedance antenna to 50 ohms by a factor of 9. This may be an improvement for a weak signal.
In practice you will be using frequencies across a wide range from MF 1mhz to possibly up to 20 mhz so unless you have a variable antenna tuner you will always have a compromise. But generally for receive only it will appear to work fine. Not having the right impedance matching simply means not having the best power transfer antenna to receiver. (that matters with transmitting but not so much with receiving).
I could not find what sort of input impedance the radio has. I note is has an antenna amplifier that can be switched in reinforcing the idea that any wire will do.
A "coax" socket does not mean always that it is designed for 50 ohms input impedance. Old car radios used to use a special "coax " connector for a wire which might seem like a coax but actually a shielded wire of very low capacitance. (might described as a high impedance coax) All this to match a perhaps 1 m rod antenna on 1 mhz mW signal. They often ahd an adjustable capacitor so you could tune it to specific antenna and cable arrangements.
So after all that waffle just connect to a wire or rod/whip longer the better. If you have a local interference source on the boat you may benefit by using a shielded wire or coax just to stop it picking up from inside the cabin. ol'will

 

[Motor_Sailor]

Try anything! We simply connected the whip aerial on top of our little Sony to the aluminium curtain rails using a crocodile clip.

 

[BrianH]

I too have the excellent Lowe HF-150 on board - bought it from a forumite many years ago.

It lives unobtrusively in a locker over the chart table and the aerial is a straightened wire coat-hanger poked into the antenna socket and which lies horizontally in that same locker running under the side deck. World-wide reception is outstanding.
.