Downeast Microwave 10GHz - 144MHz Transverter

Building the Downeast Microwave 3cm-2m transverter(Edit)

News (29 oct 2012): Reception of beacon successful!

News (22 dec 2012): Reception of own transmission using Sat LNB !

Mini-update (9 jan 2013): Reception using PLL-LNB Avenger PLL321S-2

16 apr 2013: Second transverter built, testing using HP8563E

Update: First QSO done with HB9BBD during small contest

Working on making sensitivity better

First, some pictures:(Edit)

  • The transverter is in the middle, the Yaesu FT-100D acts as 144MHz IF receiver. The A32 synthesizer on the left acts as a marker generator, and transmits on 1152.022 MHz. The 9th harmonic on 10368.198 can the be received using the transverter.

  • Closeup on the .A32 and the BAS46 diode that is used to generate harmonics.

  • Top view on the opened transverter: The A32 in the lower half generates a LO of 1136 MHz. It gets multiplied on the transverter board to 10.224 GHz. The board on the top right is the control board, acting as switch for the 2m IF and as power distribution.

  • 10GHz TX / RX Relay and tiny antenna used for reception tests of the A32 marker generator. From left to right: 10GHz RF TX, 10GHz RF RX, 2m IF, PTT (Pull to ground), 13.8V, AUX (Relay driver). The hole is there for an external 10MHz reference clock BNC connector.

Full-size pictures on []

Receiving the A32 + BAS46 signal(Edit)

In theory, the signal 10.368198 should be transverted to 144.198:

(1152.022 * 9) - (1136 * 9) =

144.198 (All units MHz)

In practice, it was on 144.137, which can be explained simply by the fact that the two 10MHz TCXOs on the two A32 boards are not on the same frequency. They can be tuned, but this requires precise equipment. The temperature sensitivity is quite noticeable also. When you put your finger on the TCXO, the received tone moves a few hundred Hz in one second.

Beacon reception(Edit)

29.10.2012, 2030z: RX of HB9MPU JN47HD beacon successful!

With a small horn antenna:

Mounted on the window shutter:

A short SMA-SMA coaxial cable connects the horn antenna to the transverter RX/TX switch relay:

The FT-100, connected on the transverter 2m IF BNC, receives the HB9MPU beacon on 144.043 (10368.043 3cm QRG):

Signal strength is S7.

Until now, I have received:

  • 29.10.2012 2030z, 10368.047, HB9MPU, JN47HD/eh64f (?), S7
  • 29.10.2012 2100z, 10368.058, HB9BBD/p, JN47GA, S2

Reception of transverter transmission using Sat LNB, RTL2832 SDR USB and GNURadio(Edit)

I had a modified satellite LNB I did not use, and whose LO frequency I had measured some time ago. This LNB can be used to receive 10GHz signals, as described by EA4EOZ on his blog:

Using this satellite LNB, and a RTL2832 SDR receiver (see for more.), it is possible to receive the 10GHz transmission on a computer. The hardware used is summarised here:

Tx in CW on IF=144.031MHz, RF=10368.031MHz, down-converted to 818.031MHz.

The receive spectrum can be shown using GNURadio:

It is clear that the LO in the LNB (It's a dielectric resonant oscillator) and the oscillator in the RTL2832 (a cheap quartz) are not very stable nor accurate, which can be seen in the spectrum and in the RX frequency I had to chose (819MHz instead of 818MHz).

The GNURadio companion flowgraph is quite simple:

This shows that the transverter is able to output a signal on 10.368MHz.

Reception of PLL Sat LNB, RTL2832 SDR USB and GNURadio(Edit)

Using a PLL based Sat LNB "Avenger PLL321S-2" bought on ebay, the spectrum is much cleaner, and it's possible to receive narrow-band signals, as seen on the following figure:

The same kind of PLL-LNB is used at the WebSDR.

Some measurements with HP8563E(Edit)

16.04.2013, some measurements with a half-broken HP8563E (only works with a span smaller than 2MHz :-( )

QSO with HB9BBD(Edit)

on 05.05.2013, small QSO with HB9BBD ! I also met him before, and I learned a lot from him. Many thanks!

Replacing input MMIC(Edit)

02.11.2013: Replaced the input MMIC by a NE32484a offered by HB9BBD, adding adjustable negative voltage source for gate, and reducing drain voltage. Let's see if it brings something !

What is left to do(Edit)

An antenna: Make a better SMA to Waveguide transition (this one uses a recycled cavity which doesn't have holes at the right place). Also, build a feed and a tripod for the small dish.

(This page will be updated)

2.11.2013 HB9EGM