New Claimed World and North American Distance Record for the 120GHz Amateur Radio Allocation

2-Apr-2003

Hi all,

How do you say this?... but again....we took the efforts of Will, W0EOM, and Bob, KF6KVG, with their latest world record of 24.6km as a challenge to try and better our East Coast efforts on 120GHz.

At the same time Will & Bob were doing 24km on the band, I was working in the shack trying an active bias circuit to improve my RX mixers at 120GHz.

The results were that W4WWQ, WA4RTS and myself took to the local hills of the Blue Ridge Mountains yet again and managed a few more QSOs on 120GHz with our best DX being 30.0km.

Details of the QSO
Date: April 2, 2003
Time: 05:18z (it was a late night)
WA1ZMS/4 37-31-19.3 79-30-14.4 FM07fm
W4WWQ 37-21-09.7 79-14-20.3 FM07ji
Distance: 30.056km

WX on WA1ZMS end of QSO
Temp: 10.5C
Dew Point: 0.5C
Pressure: 876mb
RH: 50%
Loss: 1.246dB/km

WX on W4WWQ end of QSO
Temp: 16.7C
Dew Point: -0.6C
Pressure: 988mb
RH: 31%
Loss: 1.241dB/km

Another interesting point to note is that as Will and I each take our turns at bettering the other's DX, the oxygen losses will become the limiting factor in all of our efforts. While the loss due to water vapor on this band may be around .24dB/km, the loss due to oxygen is around 1dB/km. So for someone to improve a DX record of say 30km by another 10km, they will need an improvement of 14.89dB!! (2.49 for free-space loss, 2.4dB for water loss, and 10dB for oxygen loss) The above values assume a typical semi-dry atmosphere. We'll need real QRO power for DX over 60km.

So...when Will takes the record back by a km or two (and he may already have) it might seem like splitting hairs but the loss per km from oxygen is a major obstacle to overcome and the efforts are not trivial.

73,
Brian, WA1ZMS

11-Mar-2003

Hi all,

Well the competition for DX records on 120GHz is continuing.

Mother nature gave the local area a blast of cold and dry air last night. I just couldn't pass it up! (Also gave us light snow this morning.)

W4WWQ, KA4YNO and myself took to the local hills and managed three QSOs on 120GHz with our best DX being 20.6km.

Details of today's QSO
Date: March 11, 2003 Time: 03:41z W4WWQ/4 37-22-48.7 79-21-20.3 FM07hj WA1ZMS/4 37-29-46.6 79-32-15.7 FM07fl Distance: 20.631km

WX on WA1ZMS end of QSO
Temp: -2.7C Dew Point: -18.3C RH: 29% Pressure: 906mb Calculated loss: ~1.09dB/km

Interesting point to note, as the WX gets colder, the total loss per km can go up as oxygen replaces water vapor. Interesting twist for the bands near oxygen absorption lines. The same thing can happen on 75GHz at the low end of the band.

That's it for me on 120GHz. Now it's W0EOM's turn or for someone else to join the competition.

Remember, DX records are made to be broken. Had the WX not turned dry/cold here, I'd be stopped at 12km.

73,
Brian, WA1ZMS

120GHz Station Pictures from 30km QSO

A few photos of the 30km shot on 120GHz (Note the snow still on the ground!) Location at the time was on the Blue Ridge Parkway at around 4000ft elevation.

Random 120GHz Station Pictures

Close up showing 40GHz multiplier driving 120GHz mixer/tripler

Full view of station showing Freq West PLL and power supply box

Dish and feed showing flat plate sub-reflector and hobby tubing used as circular waveguide feed

WA1ZMS station set-up along Blue Ridge Parkway near Bedford, VA during 20km QSO. Gel-cel battery on ground and Icom R-7000 receiver in van (note hydrometer on top of van for taking WX data).

WA1ZMS station set-up (second camera angle)

120GHz QSO Audio Files

You can listen to a an excerpt from the 30.0km 120GHz QSO (the file is a 401kB .WAV file).
Description: "WA1ZMS de W4WWQ"

You can listen to a an excerpt from the 20.6km 120GHz QSO (the file is a 288kB .WAV file).
Description: A very weak W4WWQ sending info (needed to have him send several times with his CW keyer for me to get full exchange for QSO)