How to get on 10G moonbounce with a portable station..... Michael Kohla I did it my way! …I did it my way!

How to get on 10G moonbounce with a portable station.....

Michael Kohla

…I did it my way!

EME meeting 2013 in Örebro

What are we going to talk about now…?

• Why 10G on a DXpedition?• Preconditions to be met by the equipment• How it was realized practically• Experience gained during TK-DXpedition• Rugged solid state alternative to TWT-power• Some construction hints for your own SSPA

(pcb, FET‘s, tuning, power measurement, safety features, results achievable)


Tell me why….

• The incentive was to activate TK not only on 70 – 6 cm, but also on 10G

• No records found of anybody, who tried 10G moonbouncing portable during a DXpedition b4 M&M

• Facing a lot of problems: where to get enough (reliable, lightweight) power, what kind of antenna, which feed (circ./lin.), how to test set-up…?

• So, just taking another challenge, which is not for the whimps…


How could it work??

• No chance to use the stressed dish for 10G (6cm is the ultimate limit, aberration from parabolic shape, +/- 3mm !!!)

• Solid dish would be nice…but heavy• Compromise: modest diameter of 1.85 m• Only prime focus, although less efficiency• Fortec Star dish (Canadian make, deep drawn

metal sheets, 6 panels bolted together)• Gain 41.7 dBd @ 1.1° beamwidth


But with two dishes….

• More space in ‚Knut‘ is needed…solved: space gained by less knickers for op/2nd op

• …two separate rotators are needed• Modified another SPID-RAS with magnetic

absolute encoders• Wired all to fit with existing OE5JFL

tracking system• Mounted dish on a second tripod


Dish on test range in DL


The transverter box

• A new DB6NT-trvtr-based system was built about 6 weeks before departure to TK

• Using waterproof installation plastic box (cheap, robust) with alu chassis inside, piggy back on dish

• For EME-power (???) a 2 x poor man‘s SSPA was integrated, 2 x 22 W ->41.5 W at N-socket

• 106 MHz OCXO for improved frequency stability• Independent sequencer, steering the trvtr, SSPA

and IC-910 in shack; only 10 m Aircell7 for IF and a PTT-line to the shack, 13 V/40 A PS underneath the dish


Trvtr – box behind dish


A look inside the box


Feed development: CP septum chapperal


First test of system

• Test was run on sked with LX1DB from garden backyard 4 weeks b4 departure

• At that time it really was not sure, if 10G would be on DXpedition

• Willi could hear me right away, with YMK on circ., exchanged O / RO….some hope

• Willi made me measure CS/G with set-up, only got 3.8 dB of 4.9 dB theor. (no imag. rejection filter, only 1 coaxial LNA (0.8dB NF) at feed

• Moon noise just detectable…


Improvement on system

• Changed to linear round wg chapperal feed (LX1DB make), + 3 dB on linear stations

• Added wg rejection filter in front of RX (rejection on 6NT sufficient, but not good enough)

• Added wg LNA (selected by 6NT, 0.57 dB@ 23 dB), directly mounted on wg switch, moved coaxial LNA to trvtr box

• Measured CS/G as 4.7 dB, moon noise 0.7 dB, a repeatable system improvement two weeks b4 departure

• Had to put matchsticks in my eyes at work…


Block schematic

wg lnaDB6NT

RX

40 WSSPA

DB6NTTX

coax lna

13.8/28Vdc/dc con

28V wg switch

Sucoflex 104

106 MHzOCXO

25 AFET sw

1m Aircom plus

Sequencer

250 mW

PTT

lin.hor. feed


New feed system


Final test in garden

• Ran another sked with LX1DB one weekend b4 departure, exchanged O / 539

• Could hear OK1KIR perfectly 519 after Willi, missed a completion by seconds only due to a thuja tree in the West …

• Had to optimise counter weight balance for auto-tracking, DRIACS went mad on speed ramp-up

• Dismantled system for TK-trip….


The 10G system of TK/DL1YMK on site


Closer up…


Even closer…


Cabling…which is which with 5 bands of moonbouncing?


Results on 10G in TK

TK/DL1YMK Log 3 cm

DateTime UTC Call TX rprt RX rprt QSO # initial #

25.05.2012 1901 LX1DB O 539 1 1

28.05.2012 1539 PA0EHG O RM 2 2

" 1605 OK1KIR O RO 3 3

" 1655 LX1DB 539 539 4 /

" 1711 DL7YC RO M 5 4

" 1951 F2TU O RO 6 5

" 2046 W5LUA O RM 7 6

" 2103 W7CJO RO M 8 7


What was learnt…

• The loss in 1.1 m Aircom Plus TX-line incl. N-connectors sums up to -1.2 db, which means abt. 29 W in the feed

• WG to feed would be much better• 1.8 m dia of dish seems to be ultimate minimum on TX…

rather than on RX (nb: for REAL EME, of course)• OCXO is sufficiently stable (as learnt from trial with

K5GW…)• Coaxial systems on frontend are no good with small

dishes• Mounting trvtr on prime focus dish for portable use is

impossible• A dish of 2.4m dia would be competitive


Hints on hb SSPA‘s

• During Örebro 2012 reported on poor man‘s SSPA with salvaged FET‘s

• Meanwhile built 7 units, including a 50 W unit• Learnt a lot about:

* tuning procedure with pre-matched FET‘s, that don‘t fit qrg-wise

* mounting of pcb

*power measurement => lots of hope, little knowing


PCB

• Design by DL2AM, 50 ohm striplines w/o matching elements, onboard –Vg control, RT5870 @ 0.5 mm, available at SA6BUN

• Ok for FET‘s FLM0910-x or TIM1011-x• Off freq. devices need a lot of re-compensating by

flaking (TIM1112-x) • Rigid milled alu-box is a MUST (de-heating)• PCB for 3-stage amps MUST be glued into box with

electr. conductive epoxy (2 comp. Systems prefered), but not everywhere; cure at 120°C!!!!

• Add. M2-screws needed at points of high RF-current (flakes ‚weld‘ on there…), see picture


Hot spots on PCB

Visible :

Infrared (after 1 min 50 W out):


Mounting of critical devices

• use only small 1p C‘s, white ceramic, low ESR, high self res. freq. like Temex CHA

• if use ATC100A-> always coding face-up• remove flux

• at output striplines use 2 x 0.5 p, side by side to compensate for inductance


Mounting of FET‘s

• Make pcb flush with FET‘s, avoid any additional inductance

• Use indium-foil for heat transfer, NO silicone grease, Arctic Silber 5 will do

• Grind base of FET on 400 wet grind paper on a glass plate

• Use little compound, avoid short circuits with comp. squeezed up in gap


Reinforcing of PCB tracks

• Use additional solder on tracks carrying high DC currents

• Especially, if 17µm copper clad is used

• 3 x SI4425 need a little help for de-heating, rated Ids 12 Amps each


Flaking, on and on….• Iterative process, beginning at

input, at full expected input power!!• Before flaking: maybe 2 W out, PA

gets awfully hot, use sufficient heatsink

• Finally tune for best phase coincidence at hybrids

• Measure RF power at dump port, by making up a 10 dB attenuator


Beware of RF hazard!!

• The un-tuned SSPA will irradiate like hell, be good to your eyes, you only have two…

• At 10G even at 20 W level you will notice a sandcorn-like feeling in your eyes, if unprotected

• Use fly screen on your goggles

• Unfortunately, doesn‘t make the guy looking better….


Measuring RF power on 10G

• Used HP435A with 8481B on 25 W SSPA‘s and 8481A with cal. Narda 18G 30dB/100W on 50W PA

• Using a Narda 30 dB coupler was bad idea

• Tried 3 differend 8481A heads: got on the same SSPA results from 21 to 25.5 W with Narda attenuator…?????

• All power heads calibrated 100%....


Where to get those GaAs-FET‘s from…

• All my devices were salvaged from those Elisra TV-link amplifiers, still available on vintage markets

• If you find one: prefer the TIM1112-x ones; the TIM1112-8 has the same Ptot (60 W) as an TIM1112-15 (!?); 25 W sat. are easily achieved

• FLM 1112-8 has only Ptot = 42.8 W – the FLM will give you the power mentioned in the specs, but not more!

• A good source for small quantities of FET‘s is PA3GIE (www.gie-tv.com), a set for a 25 W SSPA will cost @ 770,-€ (DB6NT 25 W PA is 2900,- €)

• If you send me a 180 x 90 mm RT5870 / 0.5mm card, I will be happy to make a pcb for you


Tack för er uppmärksamhet !

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How to get on 10G moonbounce with a portable station..... Michael Kohla I did it my way! …I did it my way!