Within the last couple weeks, my 50A Sorensen instrument power supply has been giving up the ghost. If I would draw anything more than a 19A load, the radio would start to output hash all over the band, generating a recklessly wide signal on CW. I must say, not very good amateur practice. Since then, I’ve been looking around for a solid power supply, even finding a nice 35A rack mount Duracom at a local hamfest for $75 which I ended up kicking myself days afterwards for not buying.

My search ended while browsing some eBay auctions and was instantly introduced to the Chinese OEM-type switching supplies used in various devices and appliances. The prices were very reasonable, 30A supplies for approximately $50. How good could they really be?

I remembered hearing something early on about switching power supplies causing interference in the shack, or generating hash so loud, it would cover-up the reception of weak DX stations. I immediately started my search on eHam to see if anyone else had attempted using similar supplies and expected to hear the usual horrific war stories. I was surprised to hear something positive on the subject with many hams having gone the same direction.

Here’s a link to one of such discussion threads:
http://www.eham.net/ehamforum/smf/index.php?topic=71829.15

With that in mind I found an eBay auction for 2 units and purchased both.

View at Picasa Chinese Power Supply (S-350-12)26-Oct-2011 22:30, Apple iPhone 4, 2.8, 3.85mm, 0.067 sec, ISO 160

View at Picasa Chinese Power Supply (S-350-12)26-Oct-2011 22:30, Apple iPhone 4, 2.8, 3.85mm, 0.067 sec, ISO 200

Upon wiring up one of the supplies with Anderson power-poles leads for output DC and the stripped back end of an extra computer power cord for the input AC, I was ready to unleash my abuse. Below you will see my findings tested with a power meter used for troubleshooting electric RC airplanes. The meter displays voltage, current draw, watts and amp hours and has been a very sought after tool in my shack. I highly recommend picking one up.

The first photo shows current draw on one supply leg of a 200w Kenwood TS-480HX at 100% duty-cycle, full output. Current draw measured was 19.5A.
The second photo captures nominal output voltage of 13.24V at minimal load. 1.2A was measured with the radio on and idle. This was the maximum voltage I could get out of this supply.
The third photo indicates the voltage drop with a 19.5A load. Output only dropped .25V.

View at Picasa TS480HX Single leg current draw at 200 watts26-Oct-2011 22:16, Apple iPhone 4, 2.8, 3.85mm, 0.067 sec, ISO 200

View at Picasa Voltage, minimal load, 1.2A idle26-Oct-2011 22:16, Apple iPhone 4, 2.8, 3.85mm, 0.067 sec, ISO 160

View at Picasa Approximate .25 voltage drop at 19.5 amp load26-Oct-2011 22:16, Apple iPhone 4, 2.8, 3.85mm, 0.067 sec, ISO 200

OK so it looks like the supply will do 20A fairly easy. But will it output it’s rated 29A? I was able to draw the radio’s maximum current draw from just one supply. This is probably a bad idea but it does seem to do it.

View at Picasa 26-Oct-2011 22:56, Apple iPhone 4, 2.8, 3.85mm, 0.067 sec, ISO 160

In addition to testing the supply on the bench with an oscilloscope (which output a clean DC trace), I also tested it with the 480HX at full output on CW. Not a hint of RF hash was detected.

I’m only a couple days on the new supplies and I’m very happy with my decision to go this route. The RF hash issues with these types of supplies seems to be a thing of the past. Long gone as the technology has gotten better. However I did notice a voltage output difference between the two units I bought. One of them outputs 14.8V max and the other 13.6V. This doesn’t seem to be all that critical for this application, but could indicate a QC issue during manufacturing. I don’t know who made mine, since I can’t read Chinese, but similar supplies can be found on-line under the name Mega-Watt or other makes with the similar red lettering in the upper left-hand corner of the printed label.

One of the other things to keep in mind is that the terminals are exposed, a concern especially for the AC input terminals. I plan to mount mine in a 2U rack enclosure with Power-pole panel mounts, an AC switch and volt meter. That should address the electrocution any nosy cats who may exploring the shack.

Until next time, 73!
de N3QO
dit dit

Laurie, KB3SIK had seen the Kenwood TH-F6A during our most recent Project Lifesaver exercise and really liked the size of the rig compared to her TH-D7AG that I got her for Christmas. It wasn’t long before the D7 was on ebay and the F6A was enroute from Ham Radio Outlet. I was also looking into the radio as well since I’m in need of a receiver that can do 216mhz on sideband. The Project Lifesaver beacons output a minimal amount of power around the 216-217mhz band and their signature can be heard in sideband mode. It is possible to hear it on AM although what your hearing is a lack of signal, or drop of static when the beacon bursts. The usage of AM almost requires you to be within a 1/4 mile of the beacon’s location, even with a 6 element yagi.

Well it arrived today and I think I’m going to stick with my new D72A. The F6A is a little too small for me, although the fact that it can receive AM/FM/SSB and CW is a real help. Hopefully she’ll let me borrow it for our future outings. Check it out!

View at Picasa NIKON COOLPIX L100 , 3.5, 5.0mm, 0.004 sec, ISO 400	View at Picasa NIKON COOLPIX L100 , 3.5, 5.0mm, 0.007 sec, ISO 760	View at Picasa NIKON COOLPIX L100 , 3.5, 5.0mm, 0.007 sec, ISO 467
View at Picasa NIKON COOLPIX L100 , 3.5, 5.0mm, 0.01 sec, ISO 800	View at Picasa NIKON COOLPIX L100 , 3.5, 5.0mm, 0.01 sec, ISO 800	View at Picasa NIKON COOLPIX L100 , 3.5, 5.0mm, 0.011 sec, ISO 800
View at Picasa NIKON COOLPIX L100 , 3.5, 5.0mm, 0.007 sec, ISO 585

I’m not sure if I had previously posted about my acquisition of a Yaesu FT-847 or not, but in case I didn’t…

Back in September/October 2010 timeframe, I was looking to start working satellites after making contact with the International Space Station (ISS) from the car. I would end up buying a Yaesu 5400B az/el rotor, Tracking system, M2 2m circular polarized antenna and sell my Icom 746 for a Yaesu FT-847. I was set, or so I thought.

I would go on to burn out the motor twice on the 5400B rotor, with the already $1200 investment I had in the project, I would need to add an additional $900 on a 440 circular polarized antenna, and pre-amps for both. Needless to say what’s left was the 847, 2m antenna and tracking system, which most likely would go on ebay.

Recently I started getting back into digital modes, RTTY, PSK and CW and found that the 847 was quite sloppy on the receive side when trying to get selective on the station you are trying to work. With some research, I found the 847 itself had a 2.7k receive filter which was used on both SSB and CW. Quite wide for work below 170hz wide and nearby stations would end up desensing the receive causing the intended station to merely disappear.

What to do? Add filters of course! I opted to go with a different radio instead, and I’ll tell you why.

I’ve read a number of reviews about filter options for the radio including this one, which gave me hope of increasing the receive performance of the 847, although there is a fairly major flaw with the way Yaesu designed this rig. The filter that is already in place is a 2.7k and it is on full time. If I were to replace that with a 2.1 or 1.8, that would be fine for SSB phone work. Same thing with CW, drop a 250hz INRAD in the second slot and CW performance would most likely be spectacular. But what about PSK and RTTY? Both as SSB modes. Unlike the 746, there is no menu setting that I can change that would use a CW filter for SSB digital modes.

If I were to then replace the 2.7k filter with a 250hz filter for use on RTTY or PSK, the radio would then be useless for SSB Phone, because that filter would be on full time. Not exactly flexible in that respect.

So the thought was to replace this rig with a Kenwood TS-480HX and have it serve in the shack on a temporary basis, until I acquire a Flex 3000. The 480 would then go in the mobile in place of the 706 which came into the shack on the YL’s desk during the last PA QSO party.
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This morning on my way to work I was successful at receiving WT3Q’s DX packet cluster which displayed perfectly on my TM-D700. I had a weak signal some of the way causing dropped packets, but overall it worked well. I plan on spinning up an RF node in Pottstown in the next couple weeks to hopefully fill in the shadowed areas.

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