Antenna length

[Rotary]

Hi All,

Another noob question I'm afraid.

After rebuilding the rotor head on my Esky Belt CP V2, I'm gradually starting to get the feel for her.

I was wondering does the Antenna need to stay at it's full length to receive on the relevant frequency ie: 35.50 Mhz.

At the moment I have it doubled back on itself a number of times as at it's about 2 feet long.

If I cut it down, will I have to measure it out as in 1/2 wave, 1/4 wave etc or is it not really an issue at the ranges I will be flying at?

Cheers

Jim

[pchristy]

1/2 wave at 35 MHz is around 5 metres - 1/4 wave is around 2.5 metres! The aerials we use are electronically tuned to the relevant frequency - the cost is reduced efficiency.

If you shorten the aerial, you will detune it. Whether this matters is dependent on a variety of factors - how far do you fly from the Tx, how much background interference is there, etc.

If you are only flyng at indoor / park flyer type range, you can probably shorten the aerial significantly and still have plenty of range in hand. However, you will also reduce the system's immunity to electrical interference from the belt / motor / etc. This may be significant if the transmitter is flea powered, as many indoor / park type sets are.

Do a range check with the model clamped to a work-mate or similar, and see what you get with the normal aerial and the motor running. Then repeat the check with the aerial shortened. You will then have to make a judgement call on whether you think you have enough. Keep the bit you remove so that you can solder it back (and heat-shrink it!) if it doesn't work.

It is possible to retune receivers to work with shorter aerials and get most of the original range back, but this is not for the inexperienced!

Once a receiver is modified this way, it should NOT be used in a full-size model, without a service by a qualified engineer!

Hope this helps!

--
Pete

[Rotary]

1/2 wave at 35 MHz is around 5 metres - 1/4 wave is around 2.5 metres! The aerials we use are electronically tuned to the relevant frequency - the cost is reduced efficiency.

If you shorten the aerial, you will detune it. Whether this matters is dependent on a variety of factors - how far do you fly from the Tx, how much background interference is there, etc.

If you are only flyng at indoor / park flyer type range, you can probably shorten the aerial significantly and still have plenty of range in hand. However, you will also reduce the system's immunity to electrical interference from the belt / motor / etc. This may be significant if the transmitter is flea powered, as many indoor / park type sets are.

Do a range check with the model clamped to a work-mate or similar, and see what you get with the normal aerial and the motor running. Then repeat the check with the aerial shortened. You will then have to make a judgement call on whether you think you have enough. Keep the bit you remove so that you can solder it back (and heat-shrink it!) if it doesn't work.

It is possible to retune receivers to work with shorter aerials and get most of the original range back, but this is not for the inexperienced!

Once a receiver is modified this way, it should NOT be used in a full-size model, without a service by a qualified engineer!

Hope this helps!

--
Pete

Thanks Pete, I'll leave it be then.

atb

Jim