9cm working across the shack :-)

[radiogareth]

After collecting parts (Titanium LNB, Diplexer, Stealth amp) it was time to hook it all up and see.
Pluto on a dummy load on my cheap Linx 12C64 tablet, Express DVB driving it. MiniTioune suitably set and bingo, a picture
Now wondering if I can cobble together the LNB (with or without its concentric lens?) and my WA5VJB log-periodic onto one of my suprlus dishes. A couple of parabolic ones (one shallow one deep) or a 65cm offset.
The deeper 'green' ex-military looking dish has a f/D of 0.56 and the larger flatter dish 0.4f/D. The Log periodic is quoted as 6dBi. A stacked bi-quad would be nice and manageable too, especially if I design and print a bending jig for the wire.
All good stuff
Gareth

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[radiogareth]

I'm hoping to get out portable on 3.4 at least and have dreamed up a combined LNB/Log-periodic mount to stick on a 65CM dish.
I'd appreciate any comments about the proposal as if its seriously flawed I can just point them both in the desired direction. But a bit more gain might help......
The Log periodic sits on top of the LNB, the slot is for the coax feed underneath. The centre of the new LNB is mounted on the same axis as the smaller LNB it replaces. Dish illumination may not be ideal......

Thanks

Gareth

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[radiogareth]

** Forehead slap**
Well it printed really well and fits, but unlike the Q100 DUAL band feed, the LNB isn't going to take kindly to a focussed 10 watts on its designed input frequency.....
Never mind, I can at least modify my CAD for other LNB & Dish mount solutions.

Still learning

Gareth

[radiogareth]

In anticipation of actually transmitting something next weekend I've had the lid off my Stealth amp, thinking initially that the feed-through for the TTL control input (as seen on some) had been snapped off. Turns out it was a blanking screw! So I traced the DC input circuitry - not hard, very similar to the 13cms versions, a big FET under the logic control does the DC switching into the main amp. The ON trace goes via a 47K thick film resistor block into what looks like a pack of 2N2222 transistors. Not a lot of current there then. So I added a resistive pair (5K6 and 6K8) across the tantalum cap on the live DC feed in. This gives about 5.2 volts which I fed out to a switch via some nice cable. Add 5 volts, amp switched on.
Now to give it some drive, from DATV-Express and a Pluto, but I can't directly measure RF at 3.4GHz. I'll look at the VSWR outputs on the amp which according to the data sheet say approx 2.5V out at 37dBm = 5 watts. Using a microwave termination resistor on a heatsink as a load it all seems to be working, so I edged up the drive from Pluto. At full drive I was getting just at tad short of 3 volts out, so 'at least 5 watts'.
Is anyone else using a similar set-up?

Now I need a TX aerial, considering making up a Bi-quad for starters https://buildyourownantenna.blogspot.co ... lator.html

I have a C band PLL LNB for RX and can either dish mount that or roll it a conical horn if I can find a design to copy/get the software to run on an old 32 bit PC.
Going to be a busy week.....
Gareth

[g8gtz]

Hi Gareth

Good progress - I will be out next Saturday with 9cms at Walbury Hill near Newbury (IO91GI) which has very good takeoff up the Thames Valley - I can't think of a suitable site at the moment but will get back to you with a suggestion. Dave G8GKQ with be out near Poole, also with 9cms.

I will be using my 9cms NB transverter with about 5 watts out but also have used an LNB to receive and have a 50watt Stealth as well.

BTW - GB3HV has an output on 3408MHz (inputs on 70 and 23cms) - this could be used a test signal but also may be a problem if you get too close when trying simplex as the band is only 10MHz wide.

73
Noel

[radiogareth]

Thanks Noel, I was about to ask 'how many bands and when' - I suspect I'm being a bit hopeful to do multi-bands on my own, but I do plan to do both days subject to gear/me/vehicle serviceability.
I'm going to scout out Kings Standing car park, Ashdown Forest Latitude: 51.0514954 Longitude: 0.1003872 on Monday. There are other similar high spots along that road that may or may not offer better takeoffs so I'll try them all with a compass.

I will also have 2 watts on 5.8FM TV with a pair of flat plate 24dbis.

And maybe 2M (not in contest) and maybe 24Cm if I find my preamp kit and 13cm with a very long loop yagi - 46 elements ex Oscar XX!

Gareth

[radiogareth]

I'm playing with the Stealth amp and trying various 'radiating elements' on it, using the FWD and REV outputs as match indicators.

WIth NO drive I see 0.59 volts on FWD, 0V on REV.

Home made dummy load (microwave power resistor) shows 3.15 FWD and 1.0 REV (about 10 watts output estimated, drive is pluto at full whack).
WA5VJB Log periodic shows 3.1 Fwd, 2.1 Rev (eekk!?)
Home made double bi-quad 3.09 fwd 1.46 rev. Altering the spacing of the bi-quads from the backplane doesn't seem to make much difference.

Found this: https://www.changpuak.ch/electronics/bi ... signer.php which gives 11mm spacing from the reflector whereas this:https://buildyourownantenna.blogspot.co ... lator.html (scroll down to the single bi-quad) gives 8mm.

Thoughts/suggestions/what to try next? Penny feed? I have a handy 60(f/D=0.326) & 66cm f/D=0.4) diameter parabolic.

Thanks

Gareth