10 GHz LNB Rx converter kit


This is not the latest build information for this converter
If you are wanting the latest build information, please go to:
http://www.earf.co.uk/3cm_conv1.html


***   NEW  -   Anglesey Abbey build and alignment session  (Saturday 18th April)  details   ***


What is it?

The converter is a single box module, intended
to be used with a modern satellite LNB, for
receiving narrow band 10 GHz amateur band
signals on an HF receiver.

It converts 10 368 - 10 369 MHz down to
18 - 19 MHz.

The kit does not include the LNB, which may
be mounted seperately  (on a dish, say), or on
the converter housing itself. A mounting saddle
is provided that is suitable for LNBs with a
40mm collar.
converters
box-internal

For an explanation of how the converter works (ie, manages to cancel out the LNBs internal LO drift) have a look at the Scatterpoint article reproduced here.

The cost!

For the moment, the cost is 35, which reflects the component cost only!. It is achieved by using several reclaimed parts that would otherwise put the price up to the 50 mark. If an LNB is also required, it can be bought on ebay for less than 10 (alternatively, contact me and I will supply one with a 40mm collar for 10). Included in the price is a build/alignment day, at the new National Trust centre at Anglesey Abbey. This will be run on Sat 18th April between 10.30 and 17.00. Kits will be handed out as soon as available, so that anyone who wants build the boards up can do, and those who want to wait for the build day session can do so. In this way, we can (hopefully) reduce any bottle-necks for tools/test equipment use on the day. If you wish to leave construction till the build/alignment day, please bring a soldering iron with you.

Build information is linked here

Prior to construction, familiarise yourself with the circuit for that particular board, and try to relate it to the layout. During construction, start with the surface mount components, paying particular attention to place the tantalum capacitors in the correct polarity - see the layout drawing and confirm on the board (there is a '+' symbol etched in copper at the 'bar' end of the capacitor), as below:

tant polarity



There are only 25 sets of pcbs, and it will be first come, first served, so if you are
interested, and your name isn't on the list opposite, please email to the address
below, and I will add you
to it.

I'm afraid all the current stock of boards have now been allocated

                                             email

The majority of components are surface mount, but large lead spaced items have been
chosen where it was thought that it might be a problem for anyone new to this type of
component.  One of the reasons for holding a build/alignment day was to provide
assistance to people who might lack confidence with smd components. We will have
at least one stereo microscope available - it is suprising how much easier this makes
construction (and each kit includes a pair of tweezers!!). To give an idea of what to
expect, here is a component side photo of the most complicated board of the three
that are used:

450MHz pcb
Serial No
Destination
Notes
1
test
TR4 = RF2312
2
test
TR4 = RF2312
3
Kevin G3AAF
Guinea pig  (test of paper-work!)
4
Allan M0CBG

5
Martin G8OFA

6
Peter M0DCV

7
Andrew M0BXT

8
Peter G8KJP

9
Mike G8VCN

10
test
TR4 = BGA6489  Scratched pcb
11
David G6KWA

12
David 2E0BPX

13
Mike M0BLP

14
Dave G4HUP

15
Sam G4DDK

16
John M0ELS

17
Dave G8JKV

18
Sean M1ECY

19
Dave G3VZE

20
Dave G4FRE

21
Alan G3NYK

22
Graham G4FSG

23
Finningley

24
Finningley

25
Finningley



Suitable LNBs

Most made-for-UK-use LNBs manufactured over the last 10 years seem suitable. The known exceptions are most Grundig variants and the Skyware SX1019/S.

The following work OK:

Thomson 13553 (requires very little injection), MTI AP8-XT2EBL, Fortec FSKU-V (including the Lidl IP-401 clone that occasionally make an appearance) and the fairly ancient Cambridge G88.

13553 ae88
lidl
mti
thomson4
dx-700
Thomson 13553
Cambridge AE88
 Lidl IP-401 MTI AP8-XT2EBL Thomson Quad Supermax DX-700

Ebay provides a good source of these. Expect to pay no more than 10, including postage. If the intention is to mount the LNB on the converter box, make sure the item has a 40mm collar for mounting, since a clip for this size is included in the kit. Both the MTI and Fortec unit are suitable in this respect (the MTI and Supermax items are currenty available on ebay at under 10). If the LNB is going to be fitted to a dish, you might wish to search for the Thomson unit, since they require the least amount of injection level, allowing a longer length of interconnecting cable to be used to feed the probe. Using RG223 cable (quarter inch, double screened), you can use up to a 4m length with all of the LNBs mentioned, and up to 6 or 7m using the Thomson item.


Configuration

Remember if mounting the unit outside, that the box is not water-proof, so fit it within a second enclosure, or preferably within the false roof, if you are using a chimney mounted mast. Fitting the box within a building is also better for keeping the unit temperature more constant. You can expect the TCXO temperature dependancy to be about 250 Hz per degree C by the time it is multiplied up to 10.35 GHz. There are three differant configurations of deployment that come to mind:

integral LNB

Integral LNB


This is quite a tidy self-contained configuration, useful for general band monitoring - it's interesting what can be heard with this (remember that the LNB feed horn itself has over 10 dBd gain. I often use this in the car in combination with my IC-706).

With the 'external reference' option components fitted (not part of the stadard kit), it can be used with a 10 MHz rubidium or GPS locked standard to enable frequency measurements to be made on incoming signals (a 2ppm transceiver, such as the IC-706 will have an accuracy at 18 MHz of +-36 Hz, so quite accurate measurements are possible).



chimney

Remote use

When required to be used with an external dish mounted LNB, the converter will require waterproofing.
For a chimney mounted dish, it may be possible to locate the converter in the false roof - this will also reduce the temperature fluctuations that the unit will experience, and will minimise oscillator drift accordingly. If the converter is mounted outside, it should be placed within a second enclosure, since it isn't waterproofed.

The maximum length of interconnecting cable for the probe feed is dependant on the actual LNB in use and the type of cable used. If RG223 is employed (this is a quarter-inch double screened flexible coax, which can use SMA connectors that are readily available), this will usually be about 4 metres. However, by using the thomson 13553 LNB, it should be possible to run a 6 - 7m run successfully. The cable type and length linking the LNB IF output to the converter is much less criticle, since this is operating at a much lower frequency (618 MHz).
It obviously makes sense to put a system together at ground level first to ensure that there will be enough probe power at the LNB. As long as the noise level at the receiver increases 10 dB when the probe is brought close to the LNB, then all will be well.

The actual location of the coupling probe depends on how much signal is available after being attenuated by the interconnection cable. If a long cable run has been used, it may be necessary to put it very close to the LNB horn input, but if the run is short, it may be adequate to simply push the probe through the back of the dish. Again, try all of this at ground level first!

Part of the Scatterpoint article relates to probe placement

dishfeed

It feels as though the Thomson LNB would support 6 - 8 m of thi cable, which would be enough to run all the way from the chimney to the shack in my bungalow, which would be excellent. I will try this when I can obtain some more cable, and will also measure the loss per metre at 10.350 GHz at the same time.

chimney modified

Extended use (requires mod)

If a much longer run than that shown above is required, it is always possible to take the x23 multiplier pcb out of the converter box and mount it in its own housing near the dish. The feed coax will then be carrying a 450 MHz signal rather than the 10.35 GHz one, and the attenuation will be much less. This should allow a 25m run or more to be employed.



External reference option

Although not fitted in the standard build, components can be added to the 450 MHz multiplier pcb that allow an external 10 MHz reference to be inputed to the converter. This is useful where higher stability is required and a rubidium or GPS standard is available. Details of the changes to the 450 MHz multiplier pcb are listed here.

There is a pilot indent dot punched on the convertor housing that can be drilled out at 6.5mm to take an sma socket for connection to the reference source.