10GHz fun today (9th Nov '08)

[VK2TDN]

hi gang
Jack, VK2TRF and myself got onto a couple of small hilltops in the western sydney area today for some 10GHz
experiments. The LOS path distance of 23km between Top Ryde inner west Sydney and Sugarloaf Ridge on the
western edge of Sydney bordering the edge of the M7 motorway.

We each started with 18dB gain horn antennae with TX of +13dBm (20mW) at my end and +16dBm (40mW) at
Jack's end. Although we did try SSB, we mainly used FM for ease of signal level readings.
With this initial setup signals were full scale and full quietening. Jack added a 10dB atten which had no noticeable
effect on signal strength or readibility. Jumping up to 30db dropped his signal level to a weaker and noisy, but still
readable level, after going to 40dB of attenuation I finally lost his signal. But switching to SSB we had an ok contact!!

Removing the attenuators and going back to 40mW I disconnected my horn from the UT141 feedline and could just hear
Jack's audio. Touching the SMA centre pin with a screwdrive blade made his signal noisy but easily readable. He then
switched up to 200mW TX power into his horn and with my feedline still hanging on open air I could read his noisy signal
and when I touched the SMA centre pin with my finger his signal became almost full quietening!!.
I will have to calibrate my pinkie finger for gain at 10GHz hahahaha

I next tried an 18" pennyfeed dish which as one would expect showed good improvement over the horn antenna.
Jack and I then both went to our larger dish antennae and redid the addition of attenuators inline.
My dish is an offset feed one ( .700m x .600m). I am using a stripped satellite LNA, replacing the original probe
with a chassis mount, extended probe, SMA socket. Jack is using a .600m (2ft) dish with a pennyfeed at prime focus.

With this arrangement and running 40mW TX at his end he again added attenuation. Will all the attenuators he had,
50dB I was still able to read his signal. It was only when I added 10dB in line at my end that his signal finally disappeared.
40mW - 50 dB = 0.000004mW.

Jack's transverter is a Khune (DB6NT), 200mW nominal, he can drop to a minimum of 40mW by lowing the 144MHz drive
My Transverter is from Down East Microwave, with 20mW on TX

We are suprised / pleased with the sensitivity of the receivers in both xverters.

cheers
Dave
VK2TDN

[VK2TDN]

Hi Matt,

I bought the transverter at the Dayton Ham Fest in Ohio back in 2006.
Building the transverter didnt take too longa few weeks or so when time was available in weekends
etc. The building wasnt the difficult part .... getting the to x3 multiplier pipe cap filters tuned up was
the hard part. I think in hindsight I would next time pay the extra and get the xverter already assembled.
The initial 1136MHz LO stage was easily assembled and operational. The 1st x3 mult stage to 3408MHz was
a bit more difficult, but got there after some frustrations. The next x3 stage was the big headache. You
really need a spec analyser etc to determine if the stage is producing 2nd,3rd or 4th harmonic of 3408, ie
6816, 10224 or 13632. My old HP freq counter which has a tuneable cavity input only goes to 12.4 GHz
and I couldnt see 6816 or 10224 so had to assume that power being generated was at 13632MHz, later
confirmed on a spec an. replacing the pins in the pipe cape filters with slightly longer ones helped overcome
that prob and get the stage to resonate easier on 10.224GHz.
all in all it prob took over a year to get the project finished... mainly cuz of that final mult. stage probs, the unit
sat for months untouched till I got some testgear help.

RF switching ... I also picked up a couple of small SMA relays at Dayton...they were the 28V version being sold
for US$15.00 at the time (ohhh how I wish I had bought a handful more!!!!) At the time I didnt even realise
the DEMI xverter had provision for supplying a higher voltage for 28V relays... Good thinking DEMI!!

My first QSO on it was back in June 2008 when VK1BL Ted came up to Mt Gibraltar and I went up to Mobbs lookout
in Carlingford ... a 95km hop it was an easy contact.

Where are you located Matt ? your info is not available for viewing and the link to your homepage doesnt work

keep in touch..
cheers
Dave
VK2TDN

[VK2OMD]

... I am having enough trouble with VK5EME LO for my 23cm rig and I need to sort that out before the contest. But I got 13cm going with 100 watts

I have done battle with kit from that stable.

I helped Ted with a LO for 2400 which had a cantankerous crystal and multiplier. My suggestion is (as it was to Ted), use a spectrum analyser to see what is happening, it is risky to line these things up on a broadband power meter because they break into incorrect modes and produce output on multiple frequencies... most of the energy is on the wrong frequencies. Tuning the filter would seriously affect the crystal osc, it was a challenge getting a spectrally clean 600MHz oscillator output, it looked more like a comb generator some times.

IIRC the lineup was a 400-600MHz crystal osc module and a multiplier module.

If your kit uses that oscillator module, you may experience the same problems, look at it with a spectrum analyser when aligning it.

Owen

[VK2GG]

Hi Owen,
I am having similar problems getting my 23 cm kit going from minikits. The LO seems to be ok on my frequency meter, but I am not getting anything like the correct output after the ERA3 doubler on the transverter board itself.

Dave,
great news on the 10G experiments last Saturday.
Might see you on Mt Canobolas ( have to replace a fromt wheet bearing on the red truck first!!)

cheers,


Dan VK2GG

[VK2TDN]

Hi Owen,
I am having similar problems getting my 23 cm kit going from minikits. The LO seems to be ok on my frequency meter, but I am not getting anything like the correct output after the ERA3 doubler on the transverter board itself.
Dave,
great news on the 10G experiments last Saturday.
Might see you on Mt Canobolas ( have to replace a fromt wheet bearing on the red truck first!!)
cheers,
Dan VK2GG

Ok Dan and Matt,
also build up a mini-kits 23cm transverter some several years ago ... will have to fire it up again and
see where its operation stands, has been a couple of years cant remember what sort of pwr I got out of it was supposed
to be ~ 50mW from memory didnt have any probs with the LO tho

hope you can make it to canobolas, Dan, will bring back memories of that ATV weekend up there

cheers
Dave

[ZL1UJG]

Hi,
New on the forums,
WRT the EME65(B) oscillator.
It is important that the primary tuned circuit.( In the can or the green former) is tuned to the crystal frequency. Due to excess gain the circuit will oscillate with this 10's of MHz off. Replace the crystal temporarily with 47 ohm resistor and 100 pF (not critical) and adjust til the correct frequency can be heard on a FM tuner or similar.
Remove the R and C and replace with the crystal. It is a good move to have 390 nH or thereabouts across the crystal, as this will cancel out the stray capacitance across the crystal. I have seen spurious operation without this fitted.
Also ground the crystal case if not already done.
There are a number of other things which I have done to the EME65's that I have, but too much detail to go into here.

Wth regards to problems driving the ERA-3 in the multipliers, I have seen spurs. I dont think the ERA3's like some reactive loads on both input and outputs. I have had good success with putting ~220 ohm SMD on the inputs of problem stages. On the input side of the DC blocking capacitor!

I run the EME65's off an +8 volt regulated supply as the last stage on the EME65 (run off the +12v) can change the loading. Some changes are needed.

At a constant temp I have seen better than 1Hz stability at 1296 MHz. Over 5 to 50C I have seen +/- 50 Hz stability with a modified W6PQL heater arrangement
Still a work in progress.

Kevin
ZL1UJG

[VK2TDN]

Hi Kevin
welcome to the forum.
Interested in your comments about experiences with the EME65 LO board. will have to try some of your mods.
I, like others, have also found problems with the LO board breaking into broadband oscillation producing a
wonderful picket fence display on the Spec-an. SCAREY to say the least hahaha

vk2gg wrote:
Hi Owen,
I am having similar problems getting my 23 cm kit going from minikits. The LO seems to be ok on my frequency meter, but
I am not getting anything like the correct output after the ERA3 doubler on the transverter board itself.
Dave, great news on the 10G experiments last Saturday. Might see you on Mt Canobolas ( have to replace a front wheel
bearing on the red truck first!!)
cheers,
Dan VK2GG

hmmmm, you have to be wary with that sort of result Dan. As the freq counter will only lock onto the strongest signal it gets and you dont realise that there may be many other harmonics present at levels that could pose a problem.

Back to 10 GHz activities.....

Jack '2TRF and I did have a couple of QSO's for the JMFD several weekends ago. Jack was on Mt Tomah and I was
at Round Corner, in the Dural area. It was only a 53km distance no big challenge. Teh real challenge for the day was at
Jack's end of the link where he battled with regular heavy showers of rain..

My latest work has been with a 3 Watt 10GHz amplifier with only 15mW input. The hassles I have run into have hilited
the need for extremely good earthing between cct brd and case especially around the input/output SMA connector to
stripline interface.
The experiments continue ..... But to get at least one amplifier going quickly, I will use a Downeast Microwave amp.
kit minus the active device ( a FMM5061VF GaAs MMIC). I will use one of my own already purchased devices ....
makes purchasing the rest of the kit much less expensive.

current prices from DEMI.... (today 30-3-09)

3-3PAP 10368MHz Power Amplifier, 3W output, 23dBG SMA, Assembled on Pallet. US$325.00 ... AU$479.00 round fig
3-3PACK 10368MHz Power Amplifier, 3W output, 23dBG SMA, Complete kit wit pallet. US$225.00 ... AU$331.00
3-3PAK 10368MHz Power Amplifier, 3W output, 23dBG SMA, PC Board kit. US$165.00 ... AU$243.00

I'm just waiting for a reply to an email to DEMI, hoping to get the complete kit minus the MMIC for ~ US$80 to 90
The MMIC is currently US$110.00, which is great for 3W on 10gig its just the exchange rate thats a killer, AU$162

will keep you up with progress reports

cheers
Dave
VK2TDN

[VK2GG]

Dave,
very interesting on the various prices and packages..
cheers,

Dan 2GG

[VK2TDN]

Hey Dan,
yes indeed.
the FMM5061 is a great MMIC covers 9.5 to 13.3 GHz reasonably easily capable of 3W out with 15mW in @ 10.3GHz
how's your 10gig project going ? have you sorted out the lack of RX gain ?

cheers
Dave

[VK3HZ]

I would strongly advise you to spend the extra for the kit with pallet.

I bought one about a year ago (when the exchange rate was a bit better). As you say, the MMIC is very high gain, and any issues with earthing can lead to problems. I found that out when trying to use the MMIC as a replacement for the 14GHz MMIC in a converted Qualcomm.

The "pallet" consists of base, case and lid all drilled and tapped. You get all connectors, bolts, washers, brass shim, etc. For me, it went together easily and worked straight off.

Regards,
Dave.

[VK2TDN]

I would strongly advise you to spend the extra for the kit with pallet.
I bought one about a year ago (when the exchange rate was a bit better). As you say, the MMIC is very high gain, and any issues with earthing can lead to problems. I found that out when trying to use the MMIC as a replacement for the 14GHz MMIC in a converted Qualcomm.
The "pallet" consists of base, case and lid all drilled and tapped. You get all connectors, bolts, washers, brass shim, etc. For me, it went together easily and worked straight off.
Regards,
Dave.

Hi Dave,
Yes I have build one of the kits and they work very well but still keen to experiment and be able
to produce a stable amplifier from scratch. The kits ... although great... are very expensive at today's exchange
rate, (DB6NT even worse ... lol) and being able to find a way to produce a reliable amplifier for a more affordable
price for the masses, is the aim
I like many are NOT in the high pay class hahahaha and as they say ... necessity is the mother of invention!!!

cheers
Dave
VK2TDN

[VK4GHZ]

The "pallet" consists of base, case and lid all drilled and tapped. You get all connectors, bolts, washers, brass shim, etc. For me, it went together easily and worked straight off.

Dave, thank you, this saved me emailing DEM tonight asking what on earth the "pallet" was.
Starting to research parts for a 10GHz system now.

[VK3TPR]

This DownEast Microwave 3 watt amp kit is fairly easy to build and would be a nice add on to a VK3XDK 10GHz transverter !

3-3PACK 10368MHz Power Amplifier, 3W output, 23dBG SMA, Complete kit wit pallet. US$225.00 ... is now about $AUD225 ! ! !

I built one recently and its proved fantastic for field days.

Peter

[VK4GHZ]

This DownEast Microwave 3 watt amp kit is fairly easy to build and would be a nice add on to a VK3XDK 10GHz transverter !

Peter, my thoughts exactly!
The 10dBm output level of the VK3XDK 10GHz transverter is ideally matched to this PA, and the exchange rate makes it a great time to be buying gear from the USA.
You can get the Kuhne 5W PA off eBay for ~$450, but they need 1W of drive so that is not a direct plug n play option.

[VK3PF]

Hi all,

And that is almost exactly what we used today to work Rex VK7MO/p in QE27:
FT-817 to XDK transverter with Apollo32 LO (with LO level fractionally low) locked with a Trimble Thunderbolt,
DEM "3W" PA giving about 2 W output, all mounted in an ex-MITEC case,
to a ex-Austar offset dish via approx 2.5 m of FSJ4-50.
All nicely built and assembled by Ralph VK3WRE.

It was interesting - we were having difficulty decoding on JT65C, but signals were loud. We worked SSB with reports from Rex varying from 53 to 51.
We then went to ISCAT, and had no problems completing contacts very quickly. ISCAT signal reports in the WSJT package (not exchanged) got to 3 (+3 not -3) on peaks!

Peter VK3PF

[VK3TPR]

Peter VK3PF and others using the Apollo-32 (by DEMI) PLL synthesizer bds, the O/P is very low, about 2-3dBm although it can be increased easily !

First find the Pi attenuator on the buffer amp chip and then by add a 75 -100ohms parallel SMD resistor to the current 82.5ohms at the top of the Pi.

I just soldered mine on top of the 82.5ohms and hey presto almost 7dBm output now.

Peter

[VK2TDN]

Peter VK3PF and others using the Apollo-32 (by DEMI) PLL synthesizer bds, the O/P is very low, about 2-3dBm although it can be increased easily !
Peter

Thats cuz they are initially designed for the DEM xverters that only require ~ 3dBm

As you discovered it can be increased by playing with the output pi attenuator values. Or if you need some serious output level removing all 3 resistors and linking the series resistor PCB pads. That gave me ~ 12dBm, 15mW

Dave