NJDTechnologies

Radio: it's not just a hobby, it's a way of life

Current Operating Frequency and Mode

OFF AIR - but back tonight after dark for more CW

Generally quiet but elevated geomagnetic conditions and average band conditions for late June; Typical domestic and long haul openings; A few more field day demo reports from the weekend; W5EST presents”Is HV RF necessary to a high performance 630m TX antenna?”

– Posted in: 630 Meter Daily Reports, 630 Meters

The details for June 26, 2016 can be viewed here.

IMPORTANT REMINDER: Neither 630-meters nor 2200-meters are open to amateurs in the US yet.  Please continue to be patient and let the FCC finish their processes.  Click here to view the proposed “considerate operators” frequency usage guide for 630-meters under Part-97 rules that was developed with the input of active band users.

Noise conditions were average for late June.  Stations were relatively easy to hear audibly in spite of storm noise because most lightning crashes were generally far enough apart to limit disturbances to listening.  Domestic propagation was generally normal but long haul paths seemed to suffer early compared to recent sessions but they turned around a bit later.

11-hour North American lightning summary

 

Geomagnetic conditions are currently at elevated-quiet levels.  The Bz is pointing to the South and solar wind velocities are averaging near 550 km/s.  Protons were observed at periodic elevated levels through the day but have since calmed this morning.  DST values continue along the centerline with a few brief excursions deeper into negative territory.

 

 

 

A few additional field day reports came in for MF JT65 activity during field day.  John, VE7BDQ reported Neil, W0YSE/7 / WG2XSV, over 200 times with a best signal report at -1 dB S/N.

In the East, Garry, K3SIW, reported that he “…listened from EN52ta for JT65 transmissions with 474.2 kHz USB dial frequency much of the night and logged the following. Excuse the lengthy list; had reporting to pskreporter enabled but it didn’t work for the 600-meter band, only 160 meters and above. Path length to WH2XZO is 949 km and to WI2XSV is  only 91 km. Reception was with an eprobe up 10′ in the back yard to an SDR-IQ. It was interesting to see detections fade in and out in just a couple minutes at times for WH2XZO.”  A transcript of Garry’s reports can be viewed here.

Neil, W0YSE/7 / WG2XSV, reported that “WSPR4 crashed after 0520z. But WSJTX captured Toby’s[VE7CNF] JT65 (5x) best of -15 at 0604z”

Larry, W7IUV / WH2XGP, provided reports for three WSPR stations and he received reports from seventeen unique stations.  As W7IUV, Larry, provided reports for four WSPR stations.

WH2XGP 24-hour WSPR activity (courtesy NI7J)

 

Mike, WA3TTS, reported “8 stations decoded overnight mostly on my SW EWE antenna, only three XGP decodes for best DX with the SW antenna about 250 deg vs 300 deg for NW…”  He provided the following statistics:

“Also decodes from XXP, XIQ, XRM, XSH/15, XZO, XXC.  Last SR decodes getting closer to 1100 UTC vs last week. On 2200m 70 WH2XND decodes overnight, -17 to -32. Last SR decode 10:52 UTC on 2200m vs 10:34 UTC (WH2XXC) on 630m”

Trans-Pacific report details, excluding KL7 and KH6, can be viewed here.

Hideo, JH3XCU, provided this link detailing VK -> total JA DX and VK -> JA peak S/N for the session.

Roger, VK4YB, indicates “Some increased QRN from storms in the Coral Sea. Propagation slightly improved vis a vis last night. Edgar EJTSWL is probably taking a rest day.”  He received reports from 7L1RLL4, JA3TVF, JH3XCU and TNUKJPM.

Ward, K7PO / WH2XXP, received reports from thirty unique stations including VK4YB, VK2XGJ, and ZL2BCG.

WH2XXP 24-hour WSPR activity (courtesy NI7J)

 

Even after a nap I was pretty wiped out from the weekend so I started WSPR near dark and let the system run overnight.  Most reports were located in the East with a few outliers like VE6XH and WH2XCR.  My transmission report details can be viewed here and my reception report details can be viewed here.

WG2XIQ 24-hour WSPR activity

 

Regional and continental WSPR breakdowns follow:

North American 24-hour WSPR activity

 

European 24-hour WSPR activity

 

Asian 24-hour WSPR activity

 

Oceania 24-hour WSPR activity

 

Eden, ZF1EJ, provided reports for three WSPR stations and he received reports from nine unique stations.

ZF1EJ 24-hour WSPR activity

 

Laurence, KL7L / WE2XPQ, returned to WSPR and received reports from VE7BDQ and he shared two-way reports with WH2XCR.

WE2XPQ 24-hour WSPR activity (NOTE:  He received WH2XCR – not shown)

 

Merv, K9FD/KH6 / WH2XCR, provided reports for VK3HP and VK5FQ.  He shared two-way reports with WE2XPQ, VK4YB, and ZL2BCG.  He received reports from VK2XGJ.  The two-way reports with VK4YB continued through sunrise.  Merv’s DX report details can be viewed here.

WH2XCR 24-hour WSPR activity

 

Jim, W5EST, present, “Is HV RF necessary to a high performance 630m TX antenna?“:

“Wherever TX antenna RF current of 1A or more flows through reactances XL or XC of several hundred ohms or more, we can expect high RF voltages (HV RF).  That means attention to appropriate insulators and safety protections like surrounding fencing and tree trimming.

In the USA on 630m, the FCC R&O (no ham privileges as yet) expects to hold TX power to 500w PEP (and 5w EIRP on 630m except 1w EIRP for certain parts of Alaska). At HF in USA, three times as much TX power—1500w PEP—may be what one may use as necessary to carry out the desired communication.

At HF, a 1500w PEP transmitter connected to a 75 ohm load delivers about 4.5A [=sqrt(1500/75)]. It develops about  335v rms [=sqrt(1500×75)] or 475 v peak (1.4 times as much peak voltage).  Even that calls for safety management, not to mention RF radiation  exposure safety management as well.

On 630m we get used to several RF amps also, but way more voltage–several KV of peak RF voltage.  Is that really necessary?

Suppose, just for one particular example, you have 3A RF current flowing in 1.0 ohm radiation resistance on 630m.  That’s about 4.2 volts peak RF voltage.  Even if ground resistance and all metal and skin effect resistances in the antenna system were 100 times that radiation resistance, only 420 volts peak RF voltage would be present.

Where do all the KV of 630m RF voltage develop then?  You know where—on the 630m antenna capacitance and across the loading coil of a conventional LF/MF vertical.  In general, whatever the LF/MF antenna design, the system reactances are the place to look if you want to reduce HV RF.

So, HV RF arises from the system reactances.  Antenna words like “resonated” and “high-Q” generally involve high enough reactances to bring HV RF on 630m.  Any 630m antenna is likely to involve HV RF when it uses ground as if it were one plate of a capacitor.

Because 630m is far lower frequency than HF, 630m involves multiples of typical HF reactance values to resonate an antenna system.  In a series resonant circuit, XL = -XC at resonance.  Since capacitive reactance is usually large at this low a frequency, bingo, you get HV RF along the top hat of a 630m TX antenna and across the loading coil as well.

Is high performance on 630m even possible without the reactances that produce HV RF as their side-effect or byproduct?   Perhaps. But I think it would be a rather different category of designs than what are generally in use today, I think. Tell us your ideas!”

 


Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com)!