Simple 432MHz Operation
Created  24.8.08

Introduction

What follows is my "take" on 432MHz operation over the years. As with all my ham band operation I have never been one for large antennas, high power linears and the likes. Most times I operate with 5-10W and frequently with far less. Clearly, if you have a stack of large yagis on a 50m tower and 1kW erp you will be able to make contacts over distances I could not imagine and access modes such as EME that simply would not be possible with QRP. What I want to show is that even with a very modest antenna and a few watts (or milliwatts) the band is still capable of great results and enormous fun.

70cms Links

DX distance calculator
Beacon list
UK Repeater list/info/maps

VHF Communications magazine

8el  yagi design
SOTA beam yagi for 70cms
WiMo yagi antennas
Handi-Tenna 3el yagi for 70cms
70cms Moxon antenna

 

1970s

My very first experience on the band was back in the early 1970s when I first came up to Cambridge. Having no equipment for the band I built a passive tripler using a varicap diode and simple down-converter based on a design in VHF Communications magazine. With my homebrew 2m AM transmitter which put out 500mW I was able to achieve 100mW output on 70cms. On receive the passive mixer had about 6-7dB loss, so it was not very sensitive, but it worked. With just a 4 el yagi in my loftspace I made my first tentative contacts with local stations. Greater fun was to be had out portable and in contests the best DX with just 100mW AM and this very small yagi was all the way up to Yorkshire (G3NHE) at around 160kms. In those days a call on ANY evening from a hilltop would guarantee several contacts up to 50kms away even with such low power and simple antennas: activity was high.

1980s

In the early 1980s I owned one of the first FM321 70cms synthesised 4W FM transceivers (based on an Australian UHF CB radio) and with this plus an old Jaybeam 48el TV antenna mounted vertically on a pole and turned by hand on the side of the house I was able to work lots of local repeaters and some decent inter-G DX on FM simplex when there was "a bit of a lift on". 70cms has localised lifts every few days and that was part of the magic of the band: one day you could hear just locals and the next (in just one direction maybe) more distant repeaters or simplex stations could be heard or worked. Every day was different. Occasionally the band would be wide open and some super DX could be heard or worked.

In those days I did not have any SSB transmitting gear on the band but I did listen in contests and at other times and well recall hearing an OZ station running 10W to an HB9CV antenna and being a true 59+ signal on a small indoor beam in the bedroom. The band is excellent for tropo DXing but it is much under-used nowadays.

More Recent Times

In more recent years I have done some operation on FM (simplex and via repeaters) from home using my vertical V2000 colinear antenna and occasionally come on SSB using my 2m halo. It is extremely inefficient but does match quite well and has allowed some contacts. Using VX1 and VX2 FM handhelds some interesting QSOs have been had when out portable on clifftops in Devon. I am sure that with my Moxon coathanger yagi or a small HB9CV it would be possible to achieve some quite spectacular FM simplex DX using these little radios or similar.

In the last few months I have tried some portable 70cms SSB/CW contest operation using my Moxon 2el yagi and achieved some decent results. I am currently considering the erection of a 70cms yagi and rotator at home so that I can exploit the band for its tropo potential in lift conditions. Based on my earlier experience I believe a reasonably sited 70cms QRP station should be able to work 60-80kms or more on SSB/CW in flat conditions to similarly equipped stations. Of course, 70cms experiences lots of minor tropo enhancements so if enough stations were active the country would be criss-crossed with QSOs most days. Sadly, activity is now very limited indeed (even when conditions are good) outside of contests and activity nights.

70cms is an excellent band for portable and mountain-topping operation as the antennas are small and lightweight. See for example the SOTA beam for both 2m and 70cms.

Another bonus of 70cms is the lack of interference from TVs, SMPSUs and PCs. Compared with the HF and lower VHF bands it is positively quiet.

Finally, don't forget satellites. I have never tried working through these on 70cms but it should be quite possible with a modest station. Many of the many satellite's 70cm beacons are audible on a very simple antenna and receiver.

Beacons

A useful indicator of conditions on any band are distant and semi-distant beacons. 70cms is no exception although several UK beacons appear to be not operational at the present time. Check the beacon list to see what ones should be audible. It is quite possible some will be right on or in the noise but checking these and more distant repeaters will give you a good idea of conditions, which can vary greatly even over a few hours.

A useful antenna for beacon monitoring would be a big wheel such as the WiMo one shown above. These omni-directional horizontal polarised antennas have a few dB gain by compressing the vertical lobe. As they "see" in all directions they allow many beacons to be checked quickly.

Conclusions

Do give 432MHz SSB or simplex FM a go sometime and if you think you have no suitable antenna then turn to your wife or girlfriend's wardrobe and search out an old coat hanger. Alternatively, a small yagi can readily be made from parts available from the local DIY shop and turned either by hand or by the smallest of rotators.

If you only come on for the odd contest you will be assured of some fun and who knows you might, like me, be persuaded to erect a more permanent beam and rotator and find out what the band is REALLY good for. Even if you can only run a few watts of SSB and a small beam the band has lots to offer especially in the smallest of lifts.

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