AmateurRadio.com

This past week, comments regarding an interesting new low-noise directionally-switched receive antenna popped-up on both the Topband reflector and the IRCA (BCB DXers) reflector.

The new JK BevFlex-4 is reported to work very well without requiring a lot of real estate for deployment. The antenna was designed by Geoff Mendenhall, W8GNM, and Ned Mountain, WC4X.

There are several things that make this package a little different. The antenna can be configured in four basic forms: CLASSIC BEVERAGE, BEVERAGE ON GROUND (BOG) / BEVERAGE IN SOD (BIS), INVERTED EWE, or as a FLAG. What is quite different however is its flexible feedpoint allowing the antenna to be fed at any point along its length when used in the BOG or BEVERAGE configuration. The antenna is completely passive and requires no preamplification although, in some configurations, it is suggested for use above 7MHz.

Full details can be found at the JK Antennas website, as well as the manual and a FAQ page.

The FAQ sheet indicates that it will perform from LW through to 10m but the most dramatic improvement in reception from users has been noted on the lower bands. It sounds like it might make an interesting antenna for NDB DXing as well.

In the BOG form, the antenna can lay right on the ground or be buried (BIS) just below the surface using RG-6 for the actual antenna element. Other configurations allow much smaller, stealth-sized wire to be employed.

An interesting YouTube video of the antenna in action as well as an in-depth description may be viewed here:


Here is one comment from an east coast topbander:

I also bought one this year....deployed it as an EWE, as that’s all the room
I have, small lot in a subdivision.....in order to work them you need to
hear them, and once I put that up, I could hear !!! first put up as EU/VK-ZL
and worked several in the DX contest, but when the african dxpedetions were on, moved it to due east/west., and worked all of them, S01, etc.....front to back is remarkable on 160, it works ok on 80, (mine was 10ft high and 38 ft long) but really rocks on 160 !!!!, and really cuts down the line noise/static I normally hear on my transmit Inv L.

Perhaps this may be your answer for a small effective receive antenna for LW and above but even if not, their website description makes for interesting reading.

This past week, comments regarding an interesting new low-noise directionally-switched receive antenna popped-up on both the Topband reflector and the IRCA (BCB DXers) reflector.

The new JK BevFlex-4 is reported to work very well without requiring a lot of real estate for deployment. The antenna was designed by Geoff Mendenhall, W8GNM, and Ned Mountain, WC4X.

There are several things that make this package a little different. The antenna can be configured in four basic forms: CLASSIC BEVERAGE, BEVERAGE ON GROUND (BOG) / BEVERAGE IN SOD (BIS), INVERTED EWE, or as a FLAG. What is quite different however is its flexible feedpoint allowing the antenna to be fed at any point along its length when used in the BOG or BEVERAGE configuration. The antenna is completely passive and requires no preamplification although, in some configurations, it is suggested for use above 7MHz.

Full details can be found at the JK Antennas website, as well as the manual and a FAQ page.

The FAQ sheet indicates that it will perform from LW through to 10m but the most dramatic improvement in reception from users has been noted on the lower bands. It sounds like it might make an interesting antenna for NDB DXing as well.

In the BOG form, the antenna can lay right on the ground or be buried (BIS) just below the surface using RG-6 for the actual antenna element. Other configurations allow much smaller, stealth-sized wire to be employed.

An interesting YouTube video of the antenna in action as well as an in-depth description may be viewed here:


Here is one comment from an east coast topbander:

I also bought one this year....deployed it as an EWE, as that’s all the room
I have, small lot in a subdivision.....in order to work them you need to
hear them, and once I put that up, I could hear !!! first put up as EU/VK-ZL
and worked several in the DX contest, but when the african dxpedetions were on, moved it to due east/west., and worked all of them, S01, etc.....front to back is remarkable on 160, it works ok on 80, (mine was 10ft high and 38 ft long) but really rocks on 160 !!!!, and really cuts down the line noise/static I normally hear on my transmit Inv L.

Perhaps this may be your answer for a small effective receive antenna for LW and above but even if not, their website description makes for interesting reading.

My Moonrise

This week I had several days of unobstructed ocean moonrises as the Moon peaked on its monthly northern declination track. Thanks to the recent topping of my next door neighbour's large Douglas Fir, and removal of low-hanging branches, I am now able to track moonrises a little further to the south than before and can add two more EME days that were previously blocked by the large tree. All operations are on 2m JT65B mode, using a 9el Yagi and 140W output.




When I started (April 1) conditions looked as if they should be good, with lunar perigee (Moon's closest approach), degradation (background skynoise) and declination all looking favorable, but I was in for a surprise.

The rising yellow plot indicates the Earth-Moon distance growing further apart (increasing path losses) while the red plot indicates fluctuation in daily skynoise (temperature) near the moon. The blue plot indicates declination track from north to south ... for me, the higher the better.

courtesy: http://www.mmmonvhf.de/eme.php

Listening on the first two days (April 1-2) produced a few weak signals from the larger stations only and nothing from the more common '4-Yagi' stations and, no QSO's ... something was amiss. I can only attribute this to some real-time solar flaring during this two-day period and the resultant short term geomagnetic agitation the flares produced ... but almost as if the 'switch' had been flipped, the third day proved to be much different.

On day three, five new 'initials' were worked including one new state (New York) and two new DXCC countries! Truly surprising was that two of the stations worked were using just two Yagis, with both stations answering one of my 'CQ's.

Good conditions continued for the next few days, bringing my initials count from #87 to # 95, with the following stations all going into the log, turning a disappointing start into one of the best lunar sessions I have encountered:

HA6NQ, LZ2FO (two 13 el Yagis), EB5EEO, K2ZJ (two 14 el Yagis), DK5YA, S52LM, F8DO, PA5Y, SV6KRW, UA3PTW, OK1UGA.

April's operation brought  my 2m DXCC count to 29 and states worked total to 27.

SV6KRW's 4 x 8el Array

EB5EEO's 4 x 32el Cross-polarized Array (16V / 16H)

DK5YA's 4 x 22 Cross-polarized Array (11V / 11H)

As mentioned in my last EME report, I keep wondering when I will run out of stations that are able to hear my small station, forcing me to build a bigger amplifier for a few more precious db, but with the ability to occasionally work some 2-Yagi stations, the list of potential targets has increased dramatically ... perhaps the large Fir tree was a bigger attenuator than I had thought.

My Moonrise

This week I had several days of unobstructed ocean moonrises as the Moon peaked on its monthly northern declination track. Thanks to the recent topping of my next door neighbour's large Douglas Fir, and removal of low-hanging branches, I am now able to track moonrises a little further to the south than before and can add two more EME days that were previously blocked by the large tree. All operations are on 2m JT65B mode, using a 9el Yagi and 140W output.




When I started (April 1) conditions looked as if they should be good, with lunar perigee (Moon's closest approach), degradation (background skynoise) and declination all looking favorable, but I was in for a surprise.

The rising yellow plot indicates the Earth-Moon distance growing further apart (increasing path losses) while the red plot indicates fluctuation in daily skynoise (temperature) near the moon. The blue plot indicates declination track from north to south ... for me, the higher the better.

courtesy: http://www.mmmonvhf.de/eme.php

Listening on the first two days (April 1-2) produced a few weak signals from the larger stations only and nothing from the more common '4-Yagi' stations and, no QSO's ... something was amiss. I can only attribute this to some real-time solar flaring during this two-day period and the resultant short term geomagnetic agitation the flares produced ... but almost as if the 'switch' had been flipped, the third day proved to be much different.

On day three, five new 'initials' were worked including one new state (New York) and two new DXCC countries! Truly surprising was that two of the stations worked were using just two Yagis, with both stations answering one of my 'CQ's.

Good conditions continued for the next few days, bringing my initials count from #87 to # 95, with the following stations all going into the log, turning a disappointing start into one of the best lunar sessions I have encountered:

HA6NQ, LZ2FO (two 13 el Yagis), EB5EEO, K2ZJ (two 14 el Yagis), DK5YA, S52LM, F8DO, PA5Y, SV6KRW, UA3PTW, OK1UGA.

April's operation brought  my 2m DXCC count to 29 and states worked total to 27.

SV6KRW's 4 x 8el Array

EB5EEO's 4 x 32el Cross-polarized Array (16V / 16H)

DK5YA's 4 x 22 Cross-polarized Array (11V / 11H)

As mentioned in my last EME report, I keep wondering when I will run out of stations that are able to hear my small station, forcing me to build a bigger amplifier for a few more precious db, but with the ability to occasionally work some 2-Yagi stations, the list of potential targets has increased dramatically ... perhaps the large Fir tree was a bigger attenuator than I had thought.

Recent discussion on the RSGB LF Group reflector about high-powered LF / MF amplifiers brought an interesting response from Tom, DK1IS, and his unique solution.

It's no secret that a Class D / E amplifier using switching MOSFETs is a popular and reasonably inexpensive method of generating some serious RF on the LF and MF bands. Equally well-known is their propensity to gobble-up FETs should the amplifiers encounter much reactance in their output load. Most builders include some form of protection for sudden over-current or unwanted SWR excursions which will shut down the amplifier before any FETs can self-destruct. Those that don't usually end up replacing FETs.




I would venture to guess that over 90% of the transmitters now being employed on LF or MF are using switching MOSFETs in a Class D / E design but there are some amateurs using vacuum tubes to do their heavy-lifting ... and with good results.

DK1IS's beautiful homebrew amplifier is shown below. Tom provided the following description:

Hi Wolf and group,

nice to hear that someone else is thinking about this approach! I´m
content with my homemade tube PA for LF and MF which has provided
reliable service since nearly 4 years now. Only some thoughts about this
concept - I hope not to bore all those hams who are happy with their
semiconductor PAs:

Years ago I had a MOSFET PA for LF, Class B push-pull with 250 W RF. It
worked well at constant conditions, but when I had to retune the antenna
due to larger QSY or made antenna experiments there always was the
danger of blowing up these nervous semiconductors. After 4 or 5 times
changing the MOSFETS I decided to build a new PA - with tubes! Looking a
little bit anachronistic this PA is absolutely good-natured. Designed for
broadband service on LF and MF it makes no problems when changing the
antenna coarse tuning from one band to the other even when the fine
tuning isn't done yet. With my former MOSFET-PA this would have been
impossible.

I wanted to have a linear PA - this usually means class B. You have to
decide between narrow band and broad band (like an audio-amp) design.
For narrow band you can use a single-ended PA but you have to add a
resonance circuit. For broad band you should use a push-pull PA and have
to build a suitable output transformer. I opted for broad band design
because it is usable for LF and MF without changes at the PA. With this
design and sin-driving I reach a total harmonic distortion of about 5 %
at 700 W RF on a pure resistive dummy load. With the usual narrow,
narrow band antennas on LF and MF you don´t need additional filters!

Concerning the tubes: If you take the common TX tubes with plate
voltages of several kV all output circuits have rather high impedances,
that means large coils for the resonance circuits resp. large
transformer windings and very high voltages - potentially a construction
problem. This led me to the choice of 2x 4x PL519 in push-pull, a rugged
colour TV line output tube with low plate voltage and high plate
current. In this way I came down to a plate-to-plate resistance of about
1 kOhm at 600 V DC plate voltage, where you easily can build a ferrite
broad band output transformer down to 50 Ohms. A disadvantage of this
concept is that you have to give individual bias to each tube, that
means for the first start-up you have to align 8 potentiometers
carefully to nearly equal cathode currents for all the tubes. But
according to my experience this alignment remains stable over a long
time. I have inserted 1-Ohm-resistors in each cathode line and have
brought the voltage drops to 8 cinch connectors, where I can monitor the
DC component (with external filtering) as well as the real time current.
With 4 tubes in parallel per branch of course you have to take care for
self oscillations. The extensive use of bypass capacitors, ferrite beads
and parasitic chokes in the plate lines is mandatory as well as good
grounding concepts are. The tubes don´t pull control grid current (this
would even be true in class C!) but you need 3 or 4 W RF input power due
to all the ohmic loads at the tube´s control grids caused by the
individual bias paths. On the other hand this certainly helps to avoid
oscillations. You can see some pictures of this PA at https://www.qrz.com/db/DK1IS

By the way: why not to try these tubes at class D? With DC plate
voltages of perhaps 1200 V you should get a nice QRO-PA ...

Wolf, you are right: building such a PA from scratch is a time consuming
enterprise. I didn´t count the working hours but according to my lab log
the whole project took about 9 months - an adequate time for a new baby!
It was a great experience anyway.

Good luck and 73,
Tom, DK1IS

2x 4x PL519 Push-Pull

TX, power supply, RX, exciter

As 'day one' for U.S. amateurs gaining their new LF / MF bands draws closer, many are seriously thinking about building or modifying rigs to get on the air. I'm sure the use of switching MOSFET amplifiers will still reign supreme when it comes to decision-making time but with some feeling more comfortable with tube technology, especially when used for power amplifiers, I suspect we will see some interesting tube transmitters being employed as well. I'm sure that some will even seek to modify older tube rigs, knowing that a pair of 6146's can muster enough power to have plenty of fun on the new band as well.

DK1IS has provided an inspiring example of what can be done using vacuum tubes ... they certainly should not be discounted as a viable method of generating your hard-earned LF / MF ERP.

Recent discussion on the RSGB LF Group reflector about high-powered LF / MF amplifiers brought an interesting response from Tom, DK1IS, and his unique solution.

It's no secret that a Class D / E amplifier using switching MOSFETs is a popular and reasonably inexpensive method of generating some serious RF on the LF and MF bands. Equally well-known is their propensity to gobble-up FETs should the amplifiers encounter much reactance in their output load. Most builders include some form of protection for sudden over-current or unwanted SWR excursions which will shut down the amplifier before any FETs can self-destruct. Those that don't usually end up replacing FETs.




I would venture to guess that over 90% of the transmitters now being employed on LF or MF are using switching MOSFETs in a Class D / E design but there are some amateurs using vacuum tubes to do their heavy-lifting ... and with good results.

DK1IS's beautiful homebrew amplifier is shown below. Tom provided the following description:

Hi Wolf and group,

nice to hear that someone else is thinking about this approach! I´m
content with my homemade tube PA for LF and MF which has provided
reliable service since nearly 4 years now. Only some thoughts about this
concept - I hope not to bore all those hams who are happy with their
semiconductor PAs:

Years ago I had a MOSFET PA for LF, Class B push-pull with 250 W RF. It
worked well at constant conditions, but when I had to retune the antenna
due to larger QSY or made antenna experiments there always was the
danger of blowing up these nervous semiconductors. After 4 or 5 times
changing the MOSFETS I decided to build a new PA - with tubes! Looking a
little bit anachronistic this PA is absolutely good-natured. Designed for
broadband service on LF and MF it makes no problems when changing the
antenna coarse tuning from one band to the other even when the fine
tuning isn't done yet. With my former MOSFET-PA this would have been
impossible.

I wanted to have a linear PA - this usually means class B. You have to
decide between narrow band and broad band (like an audio-amp) design.
For narrow band you can use a single-ended PA but you have to add a
resonance circuit. For broad band you should use a push-pull PA and have
to build a suitable output transformer. I opted for broad band design
because it is usable for LF and MF without changes at the PA. With this
design and sin-driving I reach a total harmonic distortion of about 5 %
at 700 W RF on a pure resistive dummy load. With the usual narrow,
narrow band antennas on LF and MF you don´t need additional filters!

Concerning the tubes: If you take the common TX tubes with plate
voltages of several kV all output circuits have rather high impedances,
that means large coils for the resonance circuits resp. large
transformer windings and very high voltages - potentially a construction
problem. This led me to the choice of 2x 4x PL519 in push-pull, a rugged
colour TV line output tube with low plate voltage and high plate
current. In this way I came down to a plate-to-plate resistance of about
1 kOhm at 600 V DC plate voltage, where you easily can build a ferrite
broad band output transformer down to 50 Ohms. A disadvantage of this
concept is that you have to give individual bias to each tube, that
means for the first start-up you have to align 8 potentiometers
carefully to nearly equal cathode currents for all the tubes. But
according to my experience this alignment remains stable over a long
time. I have inserted 1-Ohm-resistors in each cathode line and have
brought the voltage drops to 8 cinch connectors, where I can monitor the
DC component (with external filtering) as well as the real time current.
With 4 tubes in parallel per branch of course you have to take care for
self oscillations. The extensive use of bypass capacitors, ferrite beads
and parasitic chokes in the plate lines is mandatory as well as good
grounding concepts are. The tubes don´t pull control grid current (this
would even be true in class C!) but you need 3 or 4 W RF input power due
to all the ohmic loads at the tube´s control grids caused by the
individual bias paths. On the other hand this certainly helps to avoid
oscillations. You can see some pictures of this PA at https://www.qrz.com/db/DK1IS

By the way: why not to try these tubes at class D? With DC plate
voltages of perhaps 1200 V you should get a nice QRO-PA ...

Wolf, you are right: building such a PA from scratch is a time consuming
enterprise. I didn´t count the working hours but according to my lab log
the whole project took about 9 months - an adequate time for a new baby!
It was a great experience anyway.

Good luck and 73,
Tom, DK1IS

2x 4x PL519 Push-Pull

TX, power supply, RX, exciter

As 'day one' for U.S. amateurs gaining their new LF / MF bands draws closer, many are seriously thinking about building or modifying rigs to get on the air. I'm sure the use of switching MOSFET amplifiers will still reign supreme when it comes to decision-making time but with some feeling more comfortable with tube technology, especially when used for power amplifiers, I suspect we will see some interesting tube transmitters being employed as well. I'm sure that some will even seek to modify older tube rigs, knowing that a pair of 6146's can muster enough power to have plenty of fun on the new band as well.

DK1IS has provided an inspiring example of what can be done using vacuum tubes ... they certainly should not be discounted as a viable method of generating your hard-earned LF / MF ERP.

5. Antenna height will be limited:

... we will require that the antennas used to transmit in these bands not exceed 60 meters in height above ground level (AGL), as ARRL proposed.

6. Regarding transmission modes, no bandwidths have been specified in order to encourage experimentation:

Consistent with our proposal in the WRC-12 NPRM,  and with the existing rules in Section 97.305 for the frequency bands below 30 MHz, we authorize amateur stations to transmit the following emission types throughout the new amateur bands: CW (international Morse code telegraphy), RTTY (narrow-band direct-printing telegraphy), data, phone, and image emissions.   These emission types provide amateur operators with maximum flexibility, and we find that additional restrictions would needlessly hinder experimentation.

7. Experimental stations appear to 'still be in business' but are encouraged to transition to the 'amateur' service:

Finally, we decline to permit previously licensed experimental stations – some of which have been authorized with significantly more radiated power than the adopted EIRP limits for these new amateur service bands – to communicate with amateur stations operating in these bands.  Amateur operations in these bands currently authorized under experimental licenses should transition their operations in accordance with the adopted rules and not circumvent such rules by use of experimental licenses.

My understanding of the R&O document is that participating parties may still file a 'Petition For Reconsideration' notification within 30 days of the R&O's publication in the Federal Register. Once these (if any) are dealt with, there are no other roadblocks preventing immediate implementation.

The document contains additional details not discussed here and makes fascinating reading for amateurs that might be looking forward to the new allocations.

This is the news that many U.S. amateurs have been waiting many years to hear! It is also good news for Canadian's operating on these bands to know that they may soon see a large increase in activity south of the border. Let's hope things continue to transpire favorably and that we will finally see the new bands become a reality.

Get those soldering irons out guys and gals!