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Thread: Antenna for qrp cw

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Posted: 2023-02-19 08:33
OM pse give some advice

Posted: 2023-02-19 12:44
Advice is easy . . .

Practicality a bit more of a challenge.

If you can hear them - that doesn't mean you can work them - expect to be missed and ignored and talked over.

A hill behind can shield you from noise. Hearing is about s/n - but the other chap you can here clearly might only be hearing nose at your signal level.

Resonate as near as you can - try not to heavily "tune" odd bits of wire - you need all the power you can get to radiate.

Balanced feeder is slightly more efficient than co-axial, and can be easy home-brew, but maybe less convenient unless you can wrap it up.

Direct your signal if you can - a slope behind will reflect; water will reflect.

End fed half wave sounds great - but matching can be a trial and loose you lots of power.

Trees can be good for height - but soak up signal.

A "magnetic loop" can radiate well and maybe doesn't involve as much in guying, getting you fewer complaints about digging up eco-grass or spearing natterjacks with your tent pegs.

Kites can get your center fed half wave up high, but watch out for power lines, farmers, countryside wardens UFO enthusiasts, bored/thorough Policeman and suspicious-foreigner spotters.

In the end - whilst you are thinking about it and looking for affordable high voltage tuning capacitors for your mag-loop, get a fishing pole, some bell wire and some guy-lines and make an inverted-V.

See Richard's how-to . . . https://www.youtube.com/watch?v=WWtJ_L2o1jo

The SOTAbeams web site might give you some ideas . . . https://www.sotabeams.co.uk/

Other stuff . . .

Consider SOTA - that's fairly QRP friendly.

Take a charger and smaller ( 1 - day ) batteries - a big heavy battery will damage something. Have three sets of batteries. Charge two-whilst using the other.

Ear buds can save battery power compared to a speaker. A resonant speaker can save battery eg. https://www.youtube.com/watch?v=MF8bk6958Hg if you are demo-ing.

Make a checklist and have separate boxes - else you will forget a power cord or a BNC-2-SMA or a gender changer or leave one behind in the grass when you go back to camp/hotel on day one of the trip.

Always have a printed copy of the full license in a view-in-the-rain polythene cover, but don't show it to anyone who isn't an offical because they won't be interested.

QRP is useful for portable light-weight equipment.

At home it is useful for cost reduction - i.e. cheaper kit, multi use of the portable rig, or no permanent shack space.

Also if you have restricted space and don't want RF burns . . .

It's also useful if you have TVI issues with the neighbours Lots of people are on fibre TV nowadays but audio systems can be affected

If you do have TVI neighbours or there are block of flats restrictions in place, then a stealth antenna will also probably have to be QRP unless you want to tune the railings on the balcony and try 500 watts to cover the losses.

In London you sometimes see wires out of upper story windows across to the nearest tree, and one block has an antenna pole nailed to the top of a tree with a feeder across the gap.


Posted: 2023-02-19 13:23
Lots of good points made there, if you can heed them then all the better!

Firstly I'd say (an old saying) 'any antenna is better than no antenna'. So, if are restricted to a base-loaded short whip and poor ground plan then is is still better than nothing (just don't be surprised with the results!).

I'm lucky to have some garden, so I have a 20 or 30 meters of thin, stranded, insulated wire running the length of my garden from an upstairs window with a 10m telescopic pole holding the middle up in the air. I use a simple L-match on the window-sill as a tuner and a counterpoise wire on the ground. The setup is very much like the kind of idea favoured by Peter Parker, VK3YE (see his videos on Youtube).

Certainly not the best antenna, but much better than nothing. Probably band-specific dipoles (similarly mounted on the pole) would be better, but this can be easily tuned to any band with no feeder loss.

I would certainly suggest that if operating from your home is difficult then, weather/time etc permitting, it can be better to go out 'into the country' where it is easier to erect antennas.

Posted: 2023-02-19 22:23
TRX Xiegu G90 with built in tuner from China


works good with CW

Coax cable M&P Airborne 5mm 20m length
(works as one radial)
telescopic mast, 13m GFK from China
13,5m wire spirally wrapped around the mast

Xiegu G90 tunes from 160 - 10m.

works on the terrace or with a stand to drive the car on

more information:
what do you want to do, mobile, at home ... ??

73 Rüdiger DD5RK

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