AmateurRadio.com

VE7SL - my original 2m EME antenna.

My recent round of 2m moonbounce activity reminded me of how much this mode has changed over the years. Back in the early 80's I decided that building a 2m eme system would be a good project for winter evenings and would keep me out of trouble for a few years. Back then, it was all CW, with a smattering of SSB reserved only for the big-boys.

Unlike today's widespread JT65B usage on eme, where signals can be many db into the noise and inaudible by ear, eme contacts could only be completed by actually copying signals that you could hear with your ears. This usually required big antennas and lots of power.

After a year and a half of evening work in my basement shop, my system was pretty much ready to go. I built a kilowatt amplifier, from the ARRL's VHF Handbook, along with its plate and screen power supplies.

2m 'Plumbers Delight' handbook amp.

The amplifier used a pair of 4CX250Rs ... a very popular tube to use then and readily available. The amplifier, when run in class-C, would put out nearly a kilowatt. All of the parts were reclaimed from surplus, purchased inexpensively at our local, long gone, 'Satellite Surplus' store on Vancouver's Main Street ... this was a goldmine of radio-only parts. Pete, the proprietor, was a real character. He had a good eye for a bargain and would buy government surplus lots of equipment and strip them for parts. He must have been well-connected as the place was full of gems ... but one dare not try and argue about prices! I saw more than one guy kicked-out for trying to work Pete down a few bucks.

My antennas (see above), as well as the large H-frame support, were also built in the basement and used all scrap aluminum from one of the numerous scrap yards that were in Vancouver at the time. The system consisted of sixteen separate 6 element NBS-styled yagis, all phased. Many of the two-dozen plus N connectors were bought at Boeing Surplus near Seattle, another interesting source of parts, also now long gone. Keeping water out of the phasing lines and connectors was a real challenge here in the rain forest and if one connector was not done exactly right, would create a lot of headaches.

The antenna took up a large portion of my small, 33'-wide suburban backyard. Pointing was all done by hand, using homemade scales to indicate elevation and azimuth angles, so that it could be pointed accurately even on cloud covered days and nights. A hand-cranked boat winch took care of elevation. I had a switch-box full of surplus VHF relays out at the antenna that protected my JFET preamp and also allowed me to compare sky and sun noise against a 50 ohm load.

Over the course of a few years, the system was employed to work many Europeans as well as North American VEs' and Ws'. The one contact that stands out memorable for me, was with UA3TCF, east of Moscow. This was because I had to aim the array directly into my two-story house, located about 20' away! The moon was very low as well, so that not much elevation was required.



I eventually found that trying to hold down a full-time high school teaching job and running sked requests at 0300 were not very compatible! It also became a lot of work just to maintain the system properly. I had met and completed my original goals and it became time to move on.

Eventually the array was broken down into smaller sections and sold to local 2m guys, along with the amplifier ... but it was a huge learning experience for me and the fact that I survived building and playing with a 2,000 volt power supply, still scares the heck out of me!

Plate & screen supply for the 2m amp.

The VHF rack with xvrtrs and amps 50mHz-432mHz.

My gal Sal adorning the 2m tower on a snowy Sunday morning.

VE7SL - my original 2m EME antenna.

My recent round of 2m moonbounce activity reminded me of how much this mode has changed over the years. Back in the early 80's I decided that building a 2m eme system would be a good project for winter evenings and would keep me out of trouble for a few years. Back then, it was all CW, with a smattering of SSB reserved only for the big-boys.

Unlike today's widespread JT65B usage on eme, where signals can be many db into the noise and inaudible by ear, eme contacts could only be completed by actually copying signals that you could hear with your ears. This usually required big antennas and lots of power.

After a year and a half of evening work in my basement shop, my system was pretty much ready to go. I built a kilowatt amplifier, from the ARRL's VHF Handbook, along with its plate and screen power supplies.

2m 'Plumbers Delight' handbook amp.

The amplifier used a pair of 4CX250Rs ... a very popular tube to use then and readily available. The amplifier, when run in class-C, would put out nearly a kilowatt. All of the parts were reclaimed from surplus, purchased inexpensively at our local, long gone, 'Satellite Surplus' store on Vancouver's Main Street ... this was a goldmine of radio-only parts. Pete, the proprietor, was a real character. He had a good eye for a bargain and would buy government surplus lots of equipment and strip them for parts. He must have been well-connected as the place was full of gems ... but one dare not try and argue about prices! I saw more than one guy kicked-out for trying to work Pete down a few bucks.

My antennas (see above), as well as the large H-frame support, were also built in the basement and used all scrap aluminum from one of the numerous scrap yards that were in Vancouver at the time. The system consisted of sixteen separate 6 element NBS-styled yagis, all phased. Many of the two-dozen plus N connectors were bought at Boeing Surplus near Seattle, another interesting source of parts, also now long gone. Keeping water out of the phasing lines and connectors was a real challenge here in the rain forest and if one connector was not done exactly right, would create a lot of headaches.

The antenna took up a large portion of my small, 33'-wide suburban backyard. Pointing was all done by hand, using homemade scales to indicate elevation and azimuth angles, so that it could be pointed accurately even on cloud covered days and nights. A hand-cranked boat winch took care of elevation. I had a switch-box full of surplus VHF relays out at the antenna that protected my JFET preamp and also allowed me to compare sky and sun noise against a 50 ohm load.

Over the course of a few years, the system was employed to work many Europeans as well as North American VEs' and Ws'. The one contact that stands out memorable for me, was with UA3TCF, east of Moscow. This was because I had to aim the array directly into my two-story house, located about 20' away! The moon was very low as well, so that not much elevation was required.



I eventually found that trying to hold down a full-time high school teaching job and running sked requests at 0300 were not very compatible! It also became a lot of work just to maintain the system properly. I had met and completed my original goals and it became time to move on.

Eventually the array was broken down into smaller sections and sold to local 2m guys, along with the amplifier ... but it was a huge learning experience for me and the fact that I survived building and playing with a 2,000 volt power supply, still scares the heck out of me!

Plate & screen supply for the 2m amp.

The VHF rack with xvrtrs and amps 50mHz-432mHz.

My gal Sal adorning the 2m tower on a snowy Sunday morning.

This Saturday as well as the next will be the annual Bruce Kelley 1929 QSO Party, otherwise known as the '1929 BK'.





It's the once a year opportunity to celebrate the sounds of early amateur radio ... only transmitters that are 'era-appropriate' are allowed to be used. More specifically, transmitters must employ tubes that were available in 1929 or earlier, and transmitters must be self-excited. No crystals allowed! Crystals were new and largely unaffordable for most hams back in the depression days.

1929 marked a real turning point in amateur radio as governments finally cracked-down on things such as frequency stability, out of band operations and re-alignment of call districts. In short, hams were henceforth required to behave themselves and to clean up their signals and methods of operation.

courtesy: http://www.arrl.org/

Although the new rules did a lot to improve things when it came to 'signal purity', there was still a long way to go ... but the wheels of improvement had been officially set in motion and the next decade would see monumental changes in both transmitter and receiver architecture, as engineers along with some particularly gifted amateurs, strove to unlock the challenges of this relatively new technology.

If you tune across the CW bands during the next two Saturday nights, you will have the rare opportunity to hear exactly what the bands must have sounded like back in the early '30s'.

For the most part you will hear single tube Hartley, Colpitts or TNT oscillators with a few two-tube MOPAs' thrown in. Many of them will suffer the same problems encountered by the boys of '29 ... chirp, drift, buzzy notes and frequency instability from antennas swaying in the wind. The MOPAs' will sound much better but some surprisingly nice-sounding signals can be heard coming from properly tuned and optimised single-tube oscillators. I recall being blown away by the lovely sounding signal I heard from such a rig when first tuning into the BK activity several years ago, only to learn that it was a self-excited Hartley using 1/4" copper tubing for the oscillator tank circuit!

The '29 watering-hole on 80m will be around 3550-3580 kilocycles (be careful not to confuse this with kilohertz!) while the early afternoon to sunset 40m activity will be found from 7100-7125 kc. There may even be a few on the very low end of 160m, later on the first Saturday night only. Although many of these transmitter styles were used on 20m and higher, BK rule-makers have wisely decided not to inflict these sounds on the present populace as it would likely keep the 'Official Observer' guys busy for several days writing pink-slips.

You can learn more about amateur radio happenings leading up to and following the 1929 crackdown in my earlier series of 'Why '29' blogs here:

Part 1
Part 2
Part 3
Part 4

Those wishing to put something together for next year's event can find everything needed here:

Introduction To Building ... '29-Style

Building '29-Style - Part 1

Building '29-Style - Part 2

Heck, there me even be time to throw something together for the following Saturday if you have a few parts and an older tube or two ... the '27 comes to mind and is readily found in many junk boxes. Maybe you know an old timer with 'lots of stuff' that could help out.

Unfortunately due to a number of coinciding events, I'll not be on-the-air for the event this year, the first one I've missed since getting in on the fun several years ago.

Courtesy: http://www.leeszuba.com/projects/

Another recent reflector question about noise mitigation for active e-probe antennas brought further incite from Roelof Bakker, PAØRDT.





I found particular interest in his method of determining if the noise is being picked up by the antenna or being introduced by the feedline. As well, Roelof suggests one of the most important aspects of homebrewing ... keeping detailed notes of all tests or changes. He also suggests maintaining a healthy outlook regarding noise and rather than getting discouraged, take on the challenge of overcoming it!

Hello all,

I have been dealing with this subject for more then 10 years now and
I am pleased to pass on what I did learn so far.

The first item to look at is noise pick up on the feed line. This
can be a coax cable or a CAT5/6/7 network cable. Looking for noise
pick up on the feed line should be done without the active antenna
connected. Otherwise everything should be the same as when using the
antenna.

Ideally the antenna should be replaced by a 50 ohm termination that
can handle the power that is supplied by the DC-power supply feeding
the antenna. However, this is not necessary to achieve good results.

I am fortunate to own a PERSEUS SDR, that besides an excellent
receiver is also a nice piece of test gear. For noise pick-up
measurements I use HF-Span that changes the PERSEUS into a 0-40 MHz
spectrum analyser with a noise floor of -112 dBm. For narrow band
measurements the PERSEUS is used with Linrad, which can provide
accurate results.

Whilst looking at noise pick-up on the cable, one can unplug all
suspect devices and check if the noise is still present.

The most effective measure is grounding the shield of the coax cable
at the bottom of the mast, but I had still noise ingress of about -
100 dBm around 15 MHz. This could be solved by moving the power
supply and interface of the antenna from the operating position to
the location of the cable entry to the house. This minimises the
length of cable inside the house before the a rf-isolating
transformer used in the interface.

It is mandatory to use a separate radio earth, isolated from the
mains earth. My PC is connected to a mains outlet with a mains earth
connection, but no other equipment in the shack is using the mains
earth. This works for me.

There is also a discussion about the use of a common mode choke
versus a rf-isolating transformer. I have tried both and they both
work. However a rf-isolating transformer is much easier (and
cheaper) to build than common mode chokes with a winding of coax
cable.

In this regard, I should mention a source of interference that is
easily overlooked: receivers. It is not uncommon to own more than
one receiver and it appears that the antenna port is often far from
clean. I am using four SDR's which are fed from a balanced Norton
amplifier / four port splitter and these produce noticeable noise.
Using four rf-isolating transformers at the outputs of the splitter
eliminated the noise. My mini-whip is feeding up to 8 receivers
(hardware) via amplifiers /splitters / rf-isolating transformers
without degrading the receiver noise floor by mutual noise ingress.

The last point is about masts. A metal mast will decrease the signal
level when the antenna is mounted close to it. A short PVC extension
mast will help. The reason I am using a non-conductive mast is a
practical one as cheap and sturdy stackable camouflage net mast
sections were and are still available in western Europe. These are
ideal for either testing antennas and for permanent installations.
Metal masts can introduce problems by being resonant at a certain
frequency and receiving noise that can be transferred to the feed
line. However, checking the feed-line as described above will make
clear if this is the case or not. If there are no problems, there is
nothing against the use of a metal mast.

As every location is different, it is no use to provide an exact
recipe to solve noise problems. I believe that a systematic approach
is mandatory; take notes etc. as it is too easy to run in circles.
By all means do measure what you are doing, otherwise you will walk
in the dark for sure.

The good news is that it is still possible to build a low noise
reception system in the city and doing so can be fun! What might
also help is to change the attitude from 'it should not be there
after all' to 'what can I do about it!'

Best regards and 73,
Roelof Bakker, pa0rdt

If you're thinking about having a listen on LF or on 630m, the e-probe antenna can be a very effective solution .... and it takes up very little space. The finer details regarding the PAØRDT active antenna may be found here and here. All previous blog postings related to this topic may be found here.

The 630m band continues to provide interesting challenges for Canadian amateurs ... be they antenna, equipment or propagation related.




Sunday night produced another flurry of excitement on the new band, further demonstrating its potential for small stations operating from the suburbs.

On Sunday evening, VE3CIQ in Carleton Place, Ontario (southwest of Ottawa), and I, completed a two-way JT9 contact, following a short exchange of the required information (and more) just after midnight, Ontario time.

courtesy: https://www.google.ca/maps/

Noting the increased east-west favorability over the past few nights, Phil and I decided to give it a shot and were delighted to cover the 2200 mile / 3500km path while Murphy was sleeping and not messing with propagation.

Rather than randomly beacon on JT9, we both set 'calling each other' messages. Although this continued for some time, the QSO only took 12 minutes to complete once I started to decode Phil's signal out west. He had been decoding me and sending signal reports for a long time before his signal eventually peaked up here for the evening. I suspect that we could have continued the contact for the remainder of the night as his signal was getting stronger and stronger as we worked.

Screen shot of QSO from VE3CIQ's end

Following our QSO, Phil sent me some information about his station. His transmitter consists of a Yaesu FT-817 driving an XKA transverter which in turn drives his homebuilt class-E amplifier. The amp consists of three switching FETs in parallel, operating at 24V and produces about 175W out.

VE3CIQ - 630m Station

VE3CIQ - Homebrew 630m Class-E Transmitter

Phil's antenna is an 'inverted-L' style ... 45' up to the top of a Pine tree and then a very very long sloping top hat wire, folded back on itself three times, in a zig-zag pattern. This use of linear-loading allows him to squeeze a near full 1/4 wave antenna into his suburban lot as well as to reduce the size of his loading coil inductance. His ground system consists of ~3,000' of buried radials. By all accounts, it seems to perform very well as his WSPR beacon was recently heard in Hawaii!

VE3CIQ - 630m Linear-loaded Antenna

Phil's station stands as yet another fine example of those living in the suburbs without a lot of room for antennas yet still able to successfully operate and explore our new 630m band. With a little ham-radio creativity, it's surprising how well a small station can perform, especially when the propagation co-operates.


Following our contact, I moved back to the WSPR section of the band and continued beaconing overnight.


Apparently Phil and I picked a good evening to run a sked as the overnight WSPR map shows it to have been the best night of the new DX season so far, with forty-four individual stations reporting my signal via the WSPRnet website.

courtesy: http://wsprnet.org/drupal/

Interest and activity on 630m continues to grow nightly, now that the DX season has arrived and the reality of a 630m ham band for U.S. amateurs grows ever closer.

courtesy: www.g0mrf.com/

Dave, GØRMF, long time LF proponent and ardent home-brewer has recently posted construction details of his new 630m transmitter.






It is a readily reproducible design that may be of interest to those looking for a transmitter capable of developing full ERP power output.

From Dave's description:

This amplifier is based on the ‘300W Class D Transmitter for 136kHz’ published by the RSGB in Radio Communication and reproduced in the LF Experimenters Handbook by Peter Dodd G3LDO.
This circuit, updated and modified for 630m, uses 2 MOSFETs in push pull driven by square-waves from a CMOS D-type flip flop. The power can be varied from around 25 to 300W by increasing the supply voltage over a 12 to 32V range. Circuits are included to protect against excessive supply current and high reflected RF power.
The amplifier is suitable for any non-linear mode. Examples include CW, QRSS, WSPR, JT-9, JT-65 and FSK.
The circuit has been built on a dedicated double-sided PCB measuring 164 x 120mm. For ease of construction 90% of the components are leaded but it has been necessary to use a few surface mount devices as the normal DIP versions of some ICs are increasingly difficult to find.

In many respects, this circuit is similar to my own homebrew transmitter which can be used on both 630 and 2200m. Although Dave has built his circuit on double-sided PCB, the project would be equally at home on one-sided board or even constructed 'Manhattan' style, the method I chose. This latter style lends itself to easy component swapping to optimize circuit performance.

VE7SL 2200m / 630m Manhattan-style Transmitter

If you are interested in the PCB approach, Dave has made the PCB available, with the needed surface mount IC's pre-soldered to the board. In addition, he has the toroids and resistors available for purchase here.

In addition, Dave's website contains several interesting circuits that might be of interest to those getting started on 630m.