23cmkit

The 23cm, 13cm and 9cm LNAs are available as a kit from G4DDK.

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Important note:
I am now supplying an additional 36R resistor as replacement for the existing R2, 22R, as well as a small piece of additional absorber.
The reason for adding these parts are that there has been a few reports of the amplifier oscillating around 16GHz when L1 is not adjusted correctly. This is a critical adjustment and there is definitely a 'sweet spot' where the performance and stability are optimum. Raising the value of R2 to 36R reduces any tendancy to oscillate and gluing the piece of absorber on the end wall of the box, low and close to L1, helps further to stabilising an errant amplifier.

When substituting 36R for the 22R it will necessary to reset the bias pot for 2.0V on the drain of TR1.
Increasing the value of R2 to 36R increases the noise figure of the pre-amplifier slightly (to typically 0.28 to 0.3dB measured here). If you need the absolute lowest nf then stick with 22R and be prepared to do a little more tweaking!

If the amplifier is oscillating then the max gain will be around 30dB and the noise figure will be between 0.5 and 1.2dB. If you don't have a spectrum analyser that goes up to 16GHz then connect a power meter, with 18GHz head, at the preamp output. The level of the oscillation will be quite low as TR2 doesn't amplify 16GHz very well. If anyone is having a problem with their 23cm pre-amp and thinks that this might be the problem, please ask and I will send you the bits.

The 13cm preamp can benefit from the use of a 10R in place of 22R in R2 position. The NF will not be affected, but gain will be slightly higher.

List of parts in the kit and
Component description.

Kit assembly notes

****The 23cm, 13cm and 9cm VLNA kit construction information has been updated frequently as I've received feedback from builders. Do check you have the latest 'build' information before commencing construction****

The kit does not include connectors. Most builders have their own ideas of what connectors they want, anyway. I can supply 2 hole flange mount SMA sockets at low cost. These are surplus sales only. The connectors are not RoHS compliant.

Currently, I am supplying the NE32584 GaAs FET for the 23cm VLNA and the ATF36077 for 13 and 9cm. This will be the situation until I am no longer able to source NE32585 GaAs FETs.

The ATF36077 is also a suitable replacement for the 325 in this pre-amplifier, although the noise figure will be marginally higher on 23cm than when using the NE325. The 1420MHz version measured 0.22dB with 36dB insertion gain using the 36077. As always, this is not a guarantee that you will achieve the same results and accurate NF measurements are notoriously difficult to make.

No construction information is supplied with the kit. Everything you need is here on my web page.

Kit price

Complete kit, including PCB, box, all semiconductors, all board mounted passive parts, wire for the input coils, feedthrough capacitors and the all-important RF absorber material.

The kits do NOT contain the SMA connectors, although female SMA connectors can be provided at additional cost.

Now, pay by PayPal. I can accept PayPal e-mail payments. Note: Paypal levies a small transaction fee. Please e-mail for details.

Nearly all the parts in the kit are manufactured outside the UK. As a result of the £ 'sinking' the bill of materials cost has gone up steeply in the last few months. For this reason I have had to increase the price of the kit to £45. For anyone purchasing outside the UK you are still able to take advantage of the excellent (for you) exchange rates.

UK Kit price £45 (Excluding P&P) from 2/1/2009

Kit, with postage and packaging, UK and mainland Europe, £47.10 for one unit. The Postage and Packaging is higher for two or more units.

UK postage rates increased on the 6 April 2009.

When purchasing by Paypal I charge in UKP. Paypal cross border transaction fee takes care of the currency conversion rate.

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Kit info