Trantec S5

[kgallen]

36 minutes ago, Lamplighter said:

To be clear, the length is critical to performance, this is the tuning of the aerial to the right frequency band.

Rule of thumb is to use quarter wavelength.

speed (of light) = frequency x wavelength (c=f x lambda)

 

For 865MHz:

3x10^8 = 865x10^6 x wavelength

wavelength = 3x10^8 / 865x10^6 = 0.35m (35cm), hence 1/4 wavelength = 8.7cm => antenna length 8.7cm

 

For 606MHz:

wavelength = 3x10^8 / 606x10^6 = 50cm, hence 1/4 wavelength = 12.5cm

Edited December 24, 2021 by kgallen

[sunray]

On 12/7/2018 at 5:32 PM, sandall said:

Trantec seem to use 1/2 wavelength centre-fed aerials on their S4.n range receivers.

No those moulded black aerials are dipoles.

[sunray]

On 12/7/2018 at 5:32 PM, sandall said:

Trantec seem to use 1/2 wavelength centre-fed aerials on their S4.n range receivers.

No those moulded black aerials are dipoles.

[sunray]

On 12/7/2018 at 5:32 PM, sandall said:

Trantec seem to use 1/2 wavelength centre-fed aerials on their S4.n range receivers.

No those moulded black aerials are dipoles.

[sunray]

4 hours ago, kgallen said:

Rule of thumb is to use quarter wavelength.

speed (of light) = frequency x wavelength (c=f x lambda)

 

For 865MHz:

3x10^8 = 865x10^6 x wavelength

wavelength = 3x10^8 / 865x10^6 = 0.35m (35cm), hence 1/4 wavelength = 8.7cm => antenna length 8.7cm

 

For 606MHz:

wavelength = 3x10^8 / 606x10^6 = 50cm, hence 1/4 wavelength = 12.5cm

In practice they tend to be a little shorter for 2 reasons;

allow for a little inside the case, and

velocity factor of copper wire is approx 0.95. so 87mm = 83mm & 125mm = 119mm

I've just measured transmit aerials as 81-82mm and 115-116mm including the brass screw and the aglet (for want of a better word)

[sandall]

1 hour ago, sunray said:

No those moulded black aerials are dipoles.

Quite, or to put it another way "1/2 wavelength centre-fed"

[sunray]

1 hour ago, sandall said:

Quite, or to put it another way "1/2 wavelength centre-fed"

Not when I was learning about aerials...

However looking at google I see that's now the way a dipole is described. I'll take it down.

Edited December 25, 2021 by sunray
OK so I'm too late to edit my previous

[Wolf124]

Ok Gents. Thanks for the discussion.  Merry Christmas to you all.

I have ordered some of this...

https://cpc.farnell.com/unbranded/20333-4/5m-black-test-lead/dp/CB00101

and will give it a try against a Trantec supplied aerial of the same length and let you know how things turn out.

[cedd]

Bit late to the party, but my own aerials are the thinnest bicycle brake cable (so quite firm/springy). I have 3d printed ends around the beltpack end and tip. 

A big word of warning about making up your own aerials. You must make sure the thread isn't biting down on to the beltpack body - it needs to bite on to the threaded insert that's soldered to the pcb. If this isn't the case then when you nip up the aerial against the body, you're trying to rip the threaded socket off of the pcb. 

[Wolf124]

Hi Cedd. Compliments of the season to you. Yes, I was very careful when choosing the M3 screw attachment to make sure that it cleared the casing and didn't put any strain on the PCB. I noticed after your previous warning earlier in this thread, that some of my secondhand units came with badly oversized bases on the aerials. The have upgraded and the boards checked for damage.

What type of solder did you use on the brake cable? I assume that you soldered then into a brass M3 fitting and heat shrinked the lot.

[cedd]

I used a silver based solder. The conductivity is poorer than leaded solder but in practice it's not seemed to be a problem. It needs to be nice and hot - I used a blowtorch. Takes forever to cool, so it's wise to have some sort of jig that'll hold everything where you need it until it's solidified. 

The bandwidth of the antenna is wider due to the thicker wire, and it will have a different velocity factor. I pruned them to the same length as my trantec originals and stuck one on the spectrum analyser/tracking generator at work. Frequency response was pretty consistent across the tunable range of my transmitters and compared pretty much identically with the trantec originals.  Given that, I didn't go much further in terms of tuning the length. I don't think it'd yield any better results. 

My printed bases shroud part of the thread, so I bought standoffs with long threads, which the printed collar covers around 5mm of. The printed collar fits through the hole in the transmitter case, and the thread that protrudes from the end is what screws in to the threaded termination inside. 

[Wolf124]

Thanks Cedd.  I am assuming that the overall length of the aerial does not include the thread which 'becomes part of the PCB' when screwed in. I have cut mine from the tip of the aerial to the 'shoulder' of the thread, where it sits up against the PCB. I don't know if I have done this correctly. I have a motley selection of aerials on my 4 different models (D2, D3, G1 & G2) of belt-pack. Some of these have been tuned to Ch65. I have worked out the length using the formula posted earlier in the thread but the lengths don't appear to coincide with what came with the transmitters!!! Admittedly, they were all second-hand so the provenance of the aerials is suspect!! I am trying to standardise them before they go into store. This is the first time that I have not been under pressure to get them on stage and working in some way.  I have even only just realised that I had two working on frequencies which I feel are too close to prevent intermodulation (826.225 & 826.050).  Just goes to show what you put up with without realising.

Edited December 27, 2021 by Wolf124

[sunray]

11 hours ago, Wolf124 said:

 I have even only just realised that I had two working on frequencies which I feel are too close to prevent intermodulation (826.225 & 826.050).  Just goes to show what you put up with without realising.

A few years back I had some kit come in for repairwith 6 receivers in CH70 spaced 200KHz in 2 blocks, something like 863.2, .4, .6, & 864.4, .6, .8 He reckons he could use all 6 simultaneousely without problems. I can't remember make etc but it made no sense to me.

[Wolf124]

8 hours ago, sunray said:

A few years back I had some kit come in for repairwith 6 receivers in CH70 spaced 200KHz in 2 blocks, something like 863.2, .4, .6, & 864.4, .6, .8 He reckons he could use all 6 simultaneousely without problems. I can't remember make etc but it made no sense to me.

Could that have been the source of his problems and why the kit came in for repair?

[Wolf124]

On a slightly different note but could be Trantec related. After watching the televised stage version of 'Anything Goes' over Christmas, I could not help but notice that the girls were wearing head mics with no visible transmitter wiring to a leg pouch etc. Is now standard to put the transmitter in the singers wig? All the girls had suspiciously large hair styles with a sort of 'bulge'. If this is the case, it is not something that I have come across before and interests me. Education required please!!