VLNA is now synonymous with the G4DDK low noise preamplifier for
23cm and 13cm. Versions are also available for 70cm and 9cm. It
stands for Very Low Noise Amplifier. The name is not unique, but
has become synonymous with the G4DDK preamp.
The VLNA has been remarkably successful since it's introduction, over lunch, at the 2007 Weinheim VHF meeting in Germany! The current serial number is now close to 2400. This does not mean that is the number sold, but it's not far off!
When developing the VLNA for 23cm EME experience was drawn from
the design of WA5AGO and work by WA5LUA (now W5LUA). My
contribution was to realise that the ATF54143 would make a better,
low noise, higher dynamic range second stage than existing
The original VLNA was meant for 23cm only. The noise matching was optimised for 1296MHz operation. It wasn't long before I discovered that the design could be stretched to 2320MHz and later to 3400MHz and down to 432MHz. All from one PCB design!
After a board redesign the Issue 2 board has been in constant production for about 10 years.
It would be unfair not to recognise the contribution by RW3BP. Sergie did some great work on the original VLNA and improved its input match, lowered the noise figure and improved its stability. However, not all of Sergie's ideas are practical from a production point of view and so the VLNA has adopted just some of his ideas including use of the MGF4919 as the first stage. In practice this has provided a lower noise figure than the previous NE32584 and a noise figure of around 0.25dB is now typical. Previously it was time consuming, but possible, to get below 0.30dB and occasionally to 0.25 and even down to 0.22dB. Now, these numbers are open to debate in view of the uncertainties of accurate and repeateably measuring such low noise figures with any great meaning. However after many hundreds of measurements in Europe, and North America, it can be claimed that 0.25dB is achievable and on-air results in EME operation have confirmed the extremely low noise figures achieved by builders of the VLNA.
VLNA9 uses a different input device in order to achieve a noise
figure of below 0.4dB.
A word of caution. The VLNA23 has a very high gain of around 37dB
at 1296MHz, with the absolute gain peak of around 40dB occuring at
about 1.05GHz. This is intentional and a result of the low noise
input arrangement. It is quite normal in low noise designs. But,
it does mean that you need to be careful when using the VLNA23 not
to pick up nearby 900MHz Mobile Base stations as the amplified
output from the VLNA may cause gain compression (blocking) in the
later stages of the receive chain. The gain of the VLNA13 and 9
are a bit lower, by about 10dB, so don't tend to suffer this
problem. The gain of the VLNA70 is deliberately tailored to be no
more than about 36dB in order to reduce blocking from nearby
digital TV transmitters. You should carefully consider whether you
need the full gain of the VLNA23 when attempting to use it with
terrestrial systems and it is recommended that a 15-20dB pad
should be inserted after the VLNA23 and before the following
receiver. This may also be necessary with the VLNA70.
So, now you are familiar with the number one 23 and 13cm
low noise preamplifier, go to the price
list and see if you would like to buy one from me. You can choose
the band, kit and how you want to pay. I don't have an on-line
shop so you will need to e-mail me to ask about
availability. e-mail at the bottom of the page. I accept
either Paypal (prefered) or bank transfer. In the case of bank
transfer I will need to send you an invoice first.
For Paypal I will ask for your callsign (if appropriate) and shipping address to be added in the Paypal payments comments box. This is for my reference, even if you have already given me these details.
Note, this is the old, original, PCB from 2007
These amplifier kits are based on the popular boards by WA5VJB.
The SPF Amplifier components are optimised for the frequency range 400 to 2400MHz
Board kits are available for SMA input and output as shown below. These boards have no provision for extra RF path filtering
The smaller cable terminated boards are in extremely short supply at present.
The SPF Amplifier performance is shown in the SPF Amp PDF
PGA Amp PCB This board is also available ready assembled, to
The PGA Amplifier kit provides a noise figure of below 0.5dB at
2m and 70cm, rising to 0.8dB at 23cm. However, the wideband
frequency response of the PGA Amplifier means that it is important
to use a filter either at the input or output of the amplifier IF
IT IS CONNECTED TO AN ANTENNA. This makes the wideband PGA
amplifier better suited to use within equipment to boost levels,
reduce noise figure or just add gain. Full details of performance
are published in the PDF
The PGA144 (described next) is a truly Contest grade 2m preamplifier and already incorporates the necessary filtering.
The PGA144 has built in gain adjustment, supply regulator,
provision for over-coax powering and SMA input and output
Please note, the PGA144 does not incorporate any antenna switching relays. You need to provide these yourself!
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