Moonraker 5/8 Wave FALSE specs claiming 4.5dBd of gain!

[BriansBrain]

The output power is set using an onboard trimmer.

A bit more info please

Can it go from 0 - 100% ?
Instead of the trimmer could I bring out three cables from the board to an external pot (is it DC controlled) ?

Thanks

Not quite 0% but close enough, it will got from about 50mW up to 10W. You could bring out three cables if you wanted, however you would first need to de-solder the SMT trimpot and then solder your three cables to the tiny solder pads. It's DC controlled. I would recommend just leaving it as it.

Thanks for the info...

[MiXiN]

Here’s my new exciter, this will beat the pcs exciters by far - no in band noise and harmonics are -70dBc. Phase noise -115dBc/Hz at 10KHz offset.

PLL reference is a TCXO temperature compensated

Power output is 10W variable, this provides enough drive for multiple pallets combined together for big power.

LCD will also give you the forward and reverser power, swr, and also the deviation.

Modulation is DC coupled and is linear and flat from 30Hz to 57KHz.

402406B1-9875-4F61-AA99-775D024892B7.jpeg

That looks mint, Gareth.

Very nice.

[mpx]

Dragging up this old thread as we made a discovery. A few months back we got our hands on one of these BM108 5/8 collinear. It turned out to be a 2m ham antenna that had been incorrectly labelled/packaged by the manufacturer. Which explains why the antenna pictured (with the coils) didn't work and had a high SWR. When we put one of these on an analyser it was awful for 88-108 but perfect at around 140MHz!

Moonraker have since released a new version, which has a low SWR at 88 when briefly checked on the analyser. Haven't tested its real-world performance yet, but the design is different, having a larger loading coil of 12 turns, followed by an 82cm rod, then 21.5 turns (over a 100mm length), then two rods connected together totalling 159cm. 3 ground radials, one of which is slightly longer and has what we think to be a loading coil (it's sealed) with an adjustable end rod. The length from connector to end is about 2.7m

The physical lengths suggest by size it is a half-wave over a quarter-wave, but electrically no doubt different due to the coils. Maybe someone can theorize what it actually might be from the coils, as we're finding it hard to believe it is a 5/8 over a 5/8

The gain quoted is still 4.5dBd, hopefully, it lives up to that claim

[teckniqs]

I don't think for one second that there's any way that it can, as I think 4.5dBd of gain is around 150% of extra power. (eg 100w = 250w ERP!).

....A pal of mine tested one of these one of these from the roof of his house on low ground and then tested a standard dipole and the signal from the dipole was a lot better, but it probably wasn't a fair test from a low height on low ground to compare them.

[mpx]

If a properly tuned twin stack can give 5dB then perhaps it can. Although maybe more like 5dBi

Did your pal check the aerial on a meter first? Was the SWR okay?

These 5/8s are probably better over flat-ish terrain or with some height above average terrain. From the roof of a house the dipole would probably get over hills and some obstructions a bit better, but 5/8 push out to the horizon more so depends on location and terrain

[teckniqs]

I think a twin stack is supposed to be more like 3dBd and about 5dBi.

....Yes the SWR was properly checked using aerial analyser and was 1.0 on SWR meter with rig but his diple was about 1.3 but stronger signal from dipole a few miles away.

Yeah I've never tried a 5/8 personally but they are supposed to be better than a dipole, or they wouldn't waste time making them!

[mpx]

Any idea what the terrain was like? Receiver at similar height, lower or higher?

The theory seems to suggest the best place for a 5/8 collinear would be on a hill overlooking a city, pushing the signal out to the horizon and down into the city, or on a tower, across flatlands. But I read here some think from a low site. I guess mileage may vary

[teckniqs]

Any idea what the terrain was like? Receiver at similar height, lower or higher?

The theory seems to suggest the best place for a 5/8 collinear would be on a hill overlooking a city, pushing the signal out to the horizon and down into the city, or on a tower, across flatlands. But I read here some think from a low site. I guess mileage may vary

The test was done from 5 miles away on low ground from TX to RX and not far off being at sea level (along flat ground), but the aerial was mounted above the gutter and not quite above the roof top.
.....But 5/8 was obviously slightly higher as mounted at the very top of the pole and it's also longer (where as the dipole is mounted half way at the centre cap so it was lower but still a bit stronger signal with higher dB readings)

[mpx]

Sounds like there were some obstructions around (houses, trees, buildings etc) and maybe the dipole getting was over those better. If both aerials cleared the roof there would be a better comparison, as it's possible the roof was reflecting the signal behind the aerial into the direction the dipole was facing, affecting the radiation pattern in such a way that there was constructive gain. Or that the roof was detuning the 5/8, as they work best when a good distance away from objects.

Maybe I'll get a chance to run a comparison at some point.

[teckniqs]

Sorry I forgot to mention that it was on the side of the roof facing directly towards the reception test area, but yes of course there were many houses in the way and this was still not a far way to properly test.