The original write-up
first set of 25 boards is here
STOCK NOW DEPLETED
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
What is it?
For an explanation of how the converter works (ie,
cancel out the LNBs internal LO drift) have a look at the
article reproduced here.
This second batch of
have been updated so that by fitting a different
frequency TCXO, a low
power transmitter exciter (-30dBm)/marker can
be be produced
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 .
Stock now depleted, with no plan
Several options are available:
a) Bare boards only - £10
There will be postage to add to these. Within the UK,
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
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.
* An alignment and testing workshop is planned for both days of the Yorkshire microwave roundtable event this coming July (2010)*
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.
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.
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.