From: Brian Justin []
Sent: 24 February 2002 03:13
To: Microwave Reflector; G3PHO Peter Day;
Subject: New DX...

Hi all-

I'd like to report what looks to be a new World, as well as North American DX record for the 241GHz band.

Earlier today, myself (WA1ZMS/4) and Pete, W4WWQ set several new DX records for the band. We first worked over a distance of 3.8km, then 6.1km, and finally 7.3km at which point we ran out of signal margin for the WX conditions at the time. (Former World record was 2km by DB6NT and NA record was 1km by W2SZ/4)

The details of the claimed 7.3km record are as follows:

Feb 23, 2002† 19:45z
WA1ZMS/4 located at 37-22-56N 79-14-43W (FM07ji)
W4WWQ/4† located at 37-21-13N 79-10-15W (FM07ji)
a location to location distance of 7.3km

WX at time of QSO was:
Temperature† 8.3 degs C
Dew Point† -2.8 degs C
Relative Humidity† 46%
Pressure† 1017 millibars
Calculated loss of 1.70 dB/km

Photos and an audio file are now be posted on

The stations used are improved versions of the ones used in Dec of 2001 for the former North American DX record. The improvements involved the phase locking of the 80.6GHz Gunn sources back to homebrew ovenized crystal oscillators. This allowed the use of FSK keyed CW and the use of a narrow band receiver IF.† The IF receivers were an Icom R-7000 and a Yeasu FT-817. The IF freq was 439.7MHz +/- some frequency drift. The ovenized crystal oscillator frequency is effectively multiplied some 2220 times to get to 241GHz! The stations were able to maintain better than 2 KHz stability over several minutes. Frequency drift was still a problem however and with weak signals several repeats of the exchanges were needed to complete the 6.1 and 7.3km QSOs.† If dryer WX comes along, better DX may be achieved.

I'd like to thank Pete, W4WWQ for his roving efforts and to WA4RTS for the loan of an R-7000 in place of him being able to assist with this weekend's QSOs, and to Jeffrey Hesler of VDI.

Brian, WA1ZMS/4


On Friday, March 1,2002, we completed several QSOs that we believe set a new North American and new world record on 75GHz.

At 12:30pm PST W0EOM completed a QSO from Mt.St.Helena, California (CM88QQ) to KF6KVG on Mt. Umunhum (CM97AE) on 47.040GHz.† Signal levels were 20+dB out of the noise. Several minutes later, W0EOM and AD6FP both completed QSOs from Mt.St.Helena to KF6KVG on Mt. Umunhum on 75.600 GHz. Once again signal levels were 20+dB out of the noise. The distance from CM88QQ to CM97AE is calculated as 175.3km.

After several false starts in arranging a record attempt, Will, W0EOM, finally got everyone to agree to go out on Friday, March 1. Will and Gary AD6FP went to Mt.St.Helena, Bob KF6KVG went to Mt. Umunhum and Lars AA6IW was in Los Altos Hills. Previous tests indicated we might have difficulty with paths longer than 160km on 75GHz so Lars was positioned 156km from the Mt.St.Helena end.

Arriving at Mt. St. Helena Will and Gary found the traditional operating spot in disarray. High winds the previous evening had caused a tower to fall partially destroying the wooden deck that is usually used by the local microwave crowd.† The winds were also still pretty high, estimated at 35 to 40mph.† After some exploration we were able to find a sheltered spot out of the wind and set up the radios.

A quick try of the 10GHz radio resulted in nothing heard from the local beacon or Larsí high power transmitter so we concluded the transverter had failed.† We were hoping to use the 10GHz signals to determine bearings to Mt.Umunum so when the radio failed things were looking dismal.† Luckily Will was able to find the signal from Bob on 47GHz with a bit of panning of the dish.† Once peaked up on 47GHz we had a good optical target to use to sight the 75GHz dishes.

The 47GHz signal levels were sufficient to allow Bob to complete the exchange using NBFM rather than CW. After aligning the 75GHz dishes on the same heading as the 47GHz dish, the 75GHz signal from Bob was quickly located on the Mt.St.Helena end. To our surprise, the 75GHz signal level was as good as the 47GHz level!† The two 75GHz contacts were quickly completed from both W0EOM and AD6FP to KF6KVG. The 75GHz signal from Mt. Umunhum peaked 23dB out of the noise with 6-8dB fades.

After working Bob on 75GHz, Will and Gary repositioned their dishes and worked Lars, AA6IW, on 75GHz at 156 Km distance (this would have previously been a 1km increase in the 75GHz world record). Signal levels from Lars on the 156km path were comparable but slightly less than the levels from Bob on a 176km path.

The equipment used at each station is as follows:

W0EOM:† 47GHz:† 60mw xmit power, 2' cassegrain dish, 4dB NF rcv.
††††††† 76GHz: 8mw xmit power, 18" cassegrain dish, 15dB NF rcv.

KF6KVG: 47GHz:† >20dbm xmit power, 2' prime focus dish, 4dB NF rcv.
††††††† 76GHz: 10mw xmit power, 1' prime focus dish, 15dB NF rcv.

AD6FP:† 76GHz:† 4mw xmit power, 3' cassegrain dish, 15dB NF rcv.

AA6IW:† 76GHz: 4mw xmit power, 18" cassegrain dish, 15dB NF rcv.

All the radios use LOs that are locked to either precision OCXOs or Rubidiums.

Weather conditions were very favorable for mm-wave propagation:

18% to 26% rel. humidity along the path. 40 to 65 degree F temperatures

On the way down Mt. St. Helena we could easily see the snow capped peaks of the Sierras over 150 miles away.† The unusually low humdity as well as the clear atmospheric conditions were major factors in making QSOs on this record path.

Best regards to all from:

Will† W0EOM
Gary† AD6FP