X band Milsat and Deep Space Set-up

S

s-band

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Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
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#1
There have been a few iterations along the way but here is some info on the X band stuff that I'm using.

The feeds are based on 28mm plumbing for 8.4GHz and 35mm for 7.5GHz. Whilst the 28mm works at 7GHz, it is a bit close to cut off for my liking. I started off with squashed pipe polarisers but switched to a more professional one for DSN from uhf-satcom. The LNA is a single CE3512K2-C1 GaAsFET from CEL which has an NF around 0.8dB (should be better). That's followed by a Miteq AFS3-08500960 from Ebay. That's got a NF of about 1.6dB. The overall system NF is about 1dB on 8.4 and 1.2dB on 7.5.

X band Milsat and Deep Space Set-up_1059028
7GHz offset feed, polariser & transition

X band Milsat and Deep Space Set-up_1059028
7GHz Scalar, polariser & LNA

The BDC comprises: An isolator to improve the match, a Wessex surplus 2 stage amp with all fets replaced by MGF 4949, 3dB splitter to feed an analyser, surplus filter, WJ M14A mixer, 2250MHz LPF & an IF amp. The LO is uses a synth from a Gilat band B Ka LNB with external reference fed from a signal generator. Initially it used the original crystal giving an LO of 9125MHz. I swap the isolators and filters to switch between bands.

X band Milsat and Deep Space Set-up_1059028 X band Milsat and Deep Space Set-up_1059028

For the back end I use an SDR (AD-Pluto, Airspy or Lime Mini) or a TBS 6983.

Useful links:
https://uhf-satcom.com/
Microwave and Millemeter-wave Experiments - L. Cupido
Madrid Deep Space Communications Complex - NASA Seguimiento Online
HORIZONS Web-Interface
 
Channel Hopper

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#2
Thanks indeed

'Yorkshires !':-rofl2

Vipersan kindly sent me a TBS card - I think the same version - a couple of years back, I had thought of using it for almost exactly the same, it currently sits within a small PC, awaiting an AMD CPU with FM2 pin configuration, but I haven't found one yet at the right price. (not that I have been looking too hard) .

I have a number of decent LNBs from a few years back, the last of the WR75 ones (CalAmp and MTI) with changes to the regulator circuitry, and with easily tunable ceramic resonators. If I go the whole hog I can machine the mechanical throats, along with the feed, to match the lower frequencies.

As of next month I should have a bit more time to go ahead with those cunning plans.
 
M

moonbase

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#3
@s-band

Thank you for posting this, its not an area I have previously considered looking at but I appreciate you sharing your work.

That plumbing feed looks like it was nicked from a distillery, I can imagine a straw coloured single malt dripping from the end.
 
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#4
@s-band

Thank you for posting this, its not an area I have previously considered looking at but I appreciate you sharing your work.

That plumbing feed looks like it was nicked from a distillery, I can imagine a straw coloured single malt dripping from the end.

8 GHz is for receiving, 7 GHz is for distilling, but if sufficiently lubricated..........

I fear it might be the common types of copper piping on the market. Perhaps lead is the new copper, easier to work with.
 
S

s-band

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My Satellite Setup
1.5m IRTE PF, Octagon OSLO external Ref., TBS6983,
Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
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SE UK
#6
I use end feed pipe fittings. Most plumbing suppliers charge stupidly high prices for the larger sizes. JTM are my favoured shop and their prices for things like large reducers, couplers & pipe are very good. Endfeed Fittings 35mm - 219mm

I forgot to say that most Milsat is LHCP & DSN is RHCP.
I also didn't mention frequency stability. It's not really a problem for milsat but for DSN the system needs to be locked to a good standard (GPS, rubidium etc) as you have to work in a very narrow bandwidth (sub-Hz). I don't use one but a lot of people consider this to be the best value: Precision Frequency Reference (GPS Clock) [GPS-CLOCK] - 150.00GBP : Leo Bodnar, Simulator Electronics

@Channel Hopper WR75 cut off it around 7.9GHz so you will need to hack the waveguide. Some LNBs use parallel line inter-stage coupling which will limit the LNA bandwidth. I'll be interested to see how you get on with the mods.
 
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#7
WR75 cut off is around 7.9GHz so you will need to hack the waveguide. Some LNBs use parallel line inter-stage coupling which will limit the LNA bandwidth. I'll be interested to see how you get on with the mods

Understood. With the earlier designs of LNB the probe can be removed completely from the casting along with the circuitry, I could then invite it to sit inside a bit of 112 sized pipe, once additional material is soldered to the correct dimensions.

I have enough experience of dielectric material to depolarise the signals, but if the worst come to the worst, one of my works colleages has a 3D printing machine to shrink and print some of the C band mechanical waveguides I have lying about.
 

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S

s-band

Specialist Contributor
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My Satellite Setup
1.5m IRTE PF, Octagon OSLO external Ref., TBS6983,
Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
My Location
SE UK
#10
Channel Hopper

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#11
The writing on the tuner can, the online reviews and TBS update information, state 'DVB S2' but the chipset detail suggests otherwise.

My concern is the limitation in the symbol rates, but can't look at a gifthorse in the mouth.


Edit - just read this review

Another working DVB-S2 Card

I might have been disingenuous.
 
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#12
I forgot to say that most Milsat is LHCP & DSN is RHCP.

Having looked at your first post imagery and the statement above, I think there might be a method of fabricating a functional probe that fits into the copper tubing using a modified 5.8 GHz antenna for quadcopters, including lead and SMA connector.

https://www.amazon.co.uk/Trifycore-...F8&qid=1539527655&sr=1-343&keywords=Trifycore

A bit of snipping and soldering of the leaves is all that is required, perhaps a couple of hours work to get the frequency to around 7.5GHz

There are other designs out there (four leaf) but they are more expensive and use stainless steel for the vanes.
 
S

s-band

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My Satellite Setup
1.5m IRTE PF, Octagon OSLO external Ref., TBS6983,
Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
My Location
SE UK
#13
Having looked at your first post imagery and the statement above, I think there might be a method of fabricating a functional probe that fits into the copper tubing using a modified 5.8 GHz antenna for quadcopters, including lead and SMA connector.
Hmm, interesting idea. I think it is designed to have a hemi or spherical pattern. In that case it will have a lot of radiation from the side. I'm not sure. Maybe it might work if you put it in a cone reflector.

One of the simplest, which works OK, is a helical. I use one on S band in a deep cup to reduce ground pick-up. The pic shows the 7.5GHz version gaffer taped to the IRTE feed point. That was my 1st go at X.
X band Milsat and Deep Space Set-up_1059966
 
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#14
I should have explained slightly better, the antenna 'leaves' would best sit at the focal point of the dish, with the cable running back to the same exit point as you have on the finished piping.

The dimensions of the clover aerial on Amazon do appear to be incorrect for 5.8GHz, I would have expected something smaller in the first place, but once trimmed to X-band frequencies would/should mean a maximum diameter of 18mm, meaning an - approximate - 9mm gap all round a 35mm piece of copper pipe.
 
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#15
S

s-band

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My Satellite Setup
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Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
My Location
SE UK
#17
This is what I based my helical feed on Modifications on the axial-mode helical antenna - IEEE Journals & Magazine (paywalled)
If you don't have an account, you'll need to use your favourite search tool to find a copy.

I'd be wary of some of the wide band, Far Eastern "LNA"s. They may work but the NF can go through the roof at the high end. It can also be a problem having such high gain out of band. Have a look at the data from Minicurcuits, Qorvo etc for actual figures. If you can find one, a used Miteq LNA is safer. They can be as low as £40-60 but working out the spec can be hard and Ebay listings can be creative. The ones I bought are AFS3-08500960-15-10P-4 which are meant to be 8.5-9.6GHz <1.5dBNF and work well down to 7GHz with a measured NF ~1.3dB.

The easiest WG feed is a 1/4 wave probe in the guide as per most LNBs. You need to scale the probe length to take account of the wavelength in the guide. Waveguide Mathematics
 
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#18
This is what I based my helical feed on Modifications on the axial-mode helical antenna - IEEE Journals & Magazine (paywalled)
If you don't have an account, you'll need to use your favourite search tool to find a copy.

I'd be wary of some of the wide band, Far Eastern "LNA"s. They may work but the NF can go through the roof at the high end. It can also be a problem having such high gain out of band. Have a look at the data from Minicurcuits, Qorvo etc for actual figures. If you can find one, a used Miteq LNA is safer. They can be as low as £40-60 but working out the spec can be hard and Ebay listings can be creative. The ones I bought are AFS3-08500960-15-10P-4 which are meant to be 8.5-9.6GHz <1.5dBNF and work well down to 7GHz with a measured NF ~1.3dB.

The easiest WG feed is a 1/4 wave probe in the guide as per most LNBs. You need to scale the probe length to take account of the wavelength in the guide. Waveguide Mathematics

Thanks, whilst I know Miteq from a few years back I have no dealings with them these days.

How is Avantech rated among the hamateurs ?
 
S

s-band

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My Satellite Setup
1.5m IRTE PF, Octagon OSLO external Ref., TBS6983,
Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
My Location
SE UK
#19
Thanks, whilst I know Miteq from a few years back I have no dealings with them these days.

How is Avantech rated among the hamateurs ?
Home: Microwave/RF components, subsystems, and SATCOM - L3 Narda-MITEQ they take credit cards

Avantek > HP > Agilent > Avago > Broadcom > all deleted now
I still use ATF10136 FETs which were designed by them and still have uses. There may be a few antique LNAs around but I don't think any would be considered good these days.
 
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Channel Hopper

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#20
Thanks. I'll continue down the LNB route for the time being.
 
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