Sunday, January 12, 2014

Apartment ham radio operation

Note that this post has had several updates below.

We've just moved in to an apartment while our home is being re-built. Naturally the challenge of continuing ham radio operation intrigues me. This particular block has a single wide balcony that is almost wide enough for a 20m dipole. I've shortened a 20m dipole by adding a few turns mid leg.

The loading coils are four turns on toilet roll centres. This simple dipole uses RG-174 thin coax both as the feed line and for the balun winding which makes it very neat and light weight.

There's a lot of metal close by and this seems to lead to rather high SWR readings and low impedance but so far reception is good and reports reasonable. The KX3 ATU is able to match without problem.

To get the antenna away from the metal I've been using a squid pole to push the balun out, making a kind of horizontal inverted V configuration.

Reports from Sunday regulars VK2BMS and VK2BLQ indicate that my signal is noticeably stronger in this configuration. The antenna is very compact and packs down for portable use.

Here's the operating position.

There are several configurations I plan to try including end drooping and folded dipoles.


This weekend I tried the Ozi-pole antenna, a very short antenna for 40m-6m operation.

On 40m it works well for reception but tuning is incredibly sharp. On 20m I had two contacts but strength was well down on the simple wire dipole above. The lesson for me is that it's best to get as much wire out there as possible and bring it to resonance with the minimum loading. The ozipole is great but doesn't take advantage of the balcony space I have available.

Here's the station this weekend.

Update: Best antenna for high rise H.F.

This weekend I've had a breakthrough. A squid pole, which is a light weight telescopic fishing rod, is poked out from the edge of our balcony and a wire fed through it's end loop. This means that the wire is dropping vertically parallel with the building but about 2m out from the side. A counter poise of about 3m is laid on the balcony.

Signals are 2-3 S points better than the dipole on the balcony and reception reports of my transmitted signal are very positive.

So far I've only tried 20m but I'm tempted to give 80m a go. The wire is black insulated multi-core and pretty hard to see, but I'm concerned that it might blow into someone's balcony below and they'll complain to building management.

Here's how it looks from the operating position.

The wire is approximately 10m long all together and I match it with an Emtech ZM-2 Z-Match tuner which can achieve an almost perfect 1.1 SWR.


caulktel said...

Looks like a fun challenge, wish I was there. 73


Peter Marks said...

Thanks Joel,

the real challenge will be 40m or, dare I even suggest it... 80m. We'll see.



Anonymous said...

Use LMR-100A ...

panda said...

Hello Peter,
The new shack has great view and I am sure you will overcome all problems.
Ian VK2IJ.

Peter Marks said...

Thanks Ian,

pretty good results so far. Lots of metal about though.


Derek HL1ZIX/KE0EYJ said...

So you were really happy with the fishing pole out the window, and the line hanging down? I want to try a similar set-up at work. We have a 10 story building, and I have a balcony with power, a table, and a nice railing on 8 and 9. I have read where others hung a tennis ball at the end of their wire to keep it from blowing around.

Can I ground to a water pipe, or similar, instead of a counterpoise?


Peter Marks said...

The line hanging down, while it matched well, did not get out well. Overall the best antenna for me was the dipole for 20m with the centre pushed out with a squid pole. The evening I put that out I had a contact with someone in Hong Kong.

John VE3IPS said...

The squid pole balcony antenna is a better way to go with a good counterpoise. Its the classic Tokyo Cliff Dweller Antenna
john ve3ips

VE3IPS said...

I concur the Squid Pole is better but I had fun making my ozipole