The threat to our 2320MHz (13cm) band from commercial interests is real, but those nice people at Ofcom have given us a the option of a full power NoV (Notice of variation) to operate between 2300 and 2302MHz. I've already modified by homebrew transverter that I use for terrestrial by adding a switchable LO between 2176 for 2320 and 2156 for 2300, but currently my DB6NT based EME system is stuck on 2320.
This afternoon I've been doing some basic tests on my DB6NT Mk3 13cm 2320MHz transverter to see if it might work on 2300MHz. The MK3 is a PLL locked transverter so simply switching in a different crystal to put the Lo at 2156 instead of 2176 is not an option as it would require a firmware change.
My simple plan is to drive it at 124MHz instead of 144MHz giving an output 20MHz lower.
I've already confirmed that the receive side works at 2304, (the US EME band) with a separate receive converter at 128MHz and I wrote about it in RadCom "GHz bands" last year
Using just a signal generator at + 18dBm as IF drive (my system's standard drive level), I measured the output from the transverter using first 144MHz, then 124MHz at the same level.
The 13cm output at 2300MHz dropped by just 4dB! Result, considering my 2320MHz PA should have more gain at 2300 that is not going to be an issue. Increasing the 124MHz drive by the same 4dB and the 2300MHz output level came back to the 2320MHz level.
I still need to check the LO leakage and the harmonic levels but it's looking really good so far and I'll do that tomorrow.
So my plan will be to build a 124MHz version of the excellent G4DDK Anglian 144MHz transverter kit allowing me to use my Elecraft K3 with suitable IF switchery on 2300 and 2320MHz TX and RX plus cross band combinations and to receive on 2304 by tuning the K3 to 32MHz. I've already verified that the K3 will receive via it's transverter ports at 32MHz with little drop off in performance.
Once it's all complete I'll write up the project for Scatterpoint
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment