10 GHz LNB Rx converter kit   - second batch.....

The original write-up for the first set of 25 boards is here


Latest news:

The 10 MHz TCXO is currently not in stock from the supplier. They should have a new delivery in early March, so I can then start shipping kits from this date.


VCXO's now arrived


block diagram

What is it? 

The converter is a collection of three pcb's, intended
to be used with a modern satellite LNB, to enable it
to receive narrow band 10 GHz amateur band
signals on an HF receiver.

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

The basic kit consists of the three bare boards and
the components to populate them.
If the recommended housing is required, I can also
supply this fully machined. I may also be able to supply
a suitable LNB, if necessary.

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.

This second batch of boards have been updated so that by fitting a different frequency TCXO, a low power transmitter exciter (-30dBm)/marker can be be produced that will tune from 10 368.000 to 10 368.200 MHz, and which is capable of NBFM or CW (FSK) operation. Details for this are here .

The cost!

Stock now depleted, with no plan to re-order.

Several options are available:

a) Bare boards only - 10
b) Bare boards plus board components - 35
c) Bare boards plus board components and drilled housing - 45
d) Bare boards plus board components and drilled housing and cables/connectors - 60

There will be postage to add to these. Within the UK, this will be 2 for the first two options and 3.50 for the last two. I prefer a cheque or Bank transfer - Paypal only by negotiation, or for anyone outside the UK, where it will be the simplest method for all concerned .

A suitable LNB can be supplied, but it depends what is available on ebay at the time as to what the price for this would be.

Build information is linked here

* An alignment and testing workshop is planned for both days of the Yorkshire microwave roundtable event this coming July (2010)*

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 LNB must have a 9.75 GHz LO, and dual 9.75/10.6 GHz are really the ones to look for to ensure that they are of recent enough coverage. These dual LO LNBs will default to the 9.75 GHz LO state when used with this converter arrangement.

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
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). 

The converter in use

Quite a number of units are in use with nothing more than an LNB attached to the housing, as per the photo at the top of this page. Most LNB's have an integral horn antenna gain of about 15 dBi, so are distinctly directional used simply as they are.

Of particular note is the amount of reference signal available from the converter. In most cases, this is some 20 dB greater than is actually required!. This is very useful, because it allows the converter box to be mounted some distance away from the LNB - the prefered situation when the LNB is attached to a dish at the top of a mast. Even using ordinary low cost twin coax of the sort used for Sky+ installations, it is usually OK to run 15m of cable for both the LNB IF output and probe feed, allowing the converter box to be located indoors in many cases.

Cheap satellite twin coax of the sort shown opposite has supprisingly low loss at 10 GHz,
and is readily available on Ebay.

The item shown is marked 'webro bskyb Twin 63-008A', and consists of a single strand
inner, within a light foam insulation. The screen is a longtitudinal aluminium tape, within
an outer tinned copper braid.

Although the cable is actually 75 ohm impedance, it will easilly fit onto RG58 crimped sma
connectors, and the mismatch associated with 50 ohm connectors has not been noticed.

I have used half a dozen such cable interconnects with lengths between 1-18 metres on
these converters, and they all seem reliable enough.

Higher frequency stability

The frequency stability of the converter is determined by the TCXO, and will remain within several KHz at 10 GHz over a temperature range of 30 deg C or
so. This may well be adequate for normal use. However, since the TCXO is running at 10 MHz, the possibility of inputing a 10 MHz signal from a better frequency reference may be considered a useful upgrade. With this in mind, tracking for circuitry to automatically dissable the internal TCXO has been added to the main pcb. Components for this are not including in the basic kit, but information is linked here for anyone who is interested in this option.