I can certainly buy a second switchmode supply for the desk, but the idea is to eliminate the horrible RFI it creates, which is why I was thinking of a linear regulated supply to replace it at the operating desk.

Are you saying that the coaxial (two-wire, plus and minus) type supplies are capable of "smart" charging like the three-wire systems?

I'd thought about building a linear regulated supply for my laptop to use at my radio desk, and save the switchmode supply for use away from the desk.   It seems simple to do using the LM338K TO-3 on a heat sink.  Input will be a 120:24v transformer.   Output for laptop is 19v at 3.4A.   The laptop power jack is a simple 2-wire coaxial affair.

Anyone tried something similar?   My only concern is whether the switchmode supply that came with the laptop has any sort of "smart" charging feature for the laptop battery using current or voltage sensing.  The labeling does not indicate so. 

For discussion:  What will an altered frequency do for radio equipment?

http://www.cbsnews.com/stories/2011/06/24/ap/tech/main20074275.shtml

Yes it will be guyed.  The top of the base section at 14 feet will be attached to my garage.  The top of the middle section will have 3 guys.  Top wind speed here is around 45 mph and greatly buffered by surrounding forest canopy so actually this thing is not likely to see anything over 25 or 30 mph wind gust.

The wind load on the HexBeam is 5 sq.ft.   with probably another .5 sq.ft. on the rotator.

Agreed.  It's not going up until I get a confident design for the base.  Have been looking for the manufacturer since last fall with no luck.

I recently acquired a small crank-up tower with no manufacturers marks and unable to find a look-alike.  It is 3 nested sections of triangular construction.

Bottom section:  14.5 ft.   8" triangular
Middle section:  14.5 ft.  6" triangular
Top section:  20.5 ft.  4" triangular

It extends to 44 feet full length.  I estimate the weight at around 100 lbs.  I plan to put a small 9-pound TV rotor and a 20 pound HexBeam on top.

Without manufacturer's recommendations, are there online calculators or a text reference for determining what I need for a concrete base?

Thanks Tom.  I read through your updated material on the "4:1 balun design and operation" subject.

Today the antenna is coming down to check for good connections at the balun and confirm wire lengths on the 20%/80% fed OCF dipole design.   As I understand, I should then experiment with different feed line lengths.  If that doesn't work, I guess it's back to the bench with the balun.

Steve

UPDATE***
I took the dipole down and measured the elements again.  27.4 and 109.6 feet - I'm good there.

Balun on the bench - - I am only able to check the balance with a 259B and it looks good there.  Checked all balun connections.

Hoisted dipole back up to 75-80 feet and nothing has changed SWR/impedance-wise.

Guess it's time to rewind to the balun and get someone with the proper test equipment to get the correct values.



 

It is a dual core 4:1 balun feeding a 20% OCF Dipole.  It is similar to BalunDesign's model 4115ocf.

It bench tested good with a 200-ohm resistor.  I'll be taking the antenna down to check connections and wire lengths.

I simply rubbed the contacts with a cloth and spit. No harm done?

Not everytime, just occasionally.  Is it harmful?  How can I correct it?

Okay - now we're getting somewhere.

The switch case is grounded to a rod 3 feet away, which is also bonded back to the shack/house system.

I am using a homemade 4:1 current balun similar to the Balun Designs design.

I connected a jumper coax to the antenna coax with a barrel and touched the barrel to the switch case and the impedance changed.  So then, I have a common mode current issue apparently.  Perhaps I should check my balun again.

I tried the other test with the dummy load through the relay.  It is 50 ohms.
So the switch should be fine, and I need to look at my balun/antenna/feedline.

I took the relay contacts apart and cleaned them.  Made sure the relays are making good mechanical contact and tried again.  No change. 

I get a good SWR dip at around 3.7 MHz with the antenna analyzer connected directly to the antenna feedline.   SWR around 3:1 at the lower band edge and 4:1 at upper band edge.

I connect the antenna feedline to one of the RCS8V antenna ports (I've tried them all with the same result), then I connect the analyzer to the common switch port with a 1-foot length of coax, and the analyzer shows a strong SWR dip at 3.2 MHz and quite high SWR's across 80m band.  The short piece of coax is good, and I've tried two other pieces as well.  All read the same.

I'm stumped.

Correction - - I meant to type 577 +j111.  Still a large bump though.

Frequency is 3.7Mhz.  Antenna is a 80m dipole at 75 feet fed with 80 feet of new RG-8X.

I am using an Ameritron RCS-8V Remote Coax Switch.
I measure the impedance (with MFJ antenna analyzer) at the end of a feedline for an antenna as 148 +j8.
I then attach that same coax to one of the RCS-8V "antenna" connectors, and then measure the impedance at the common coax connector of the RCS-8V as 1577 + j111.

The only difference in the measurement lash-up is the RCS-8V relay circuit and a 1-foot piece of coax from the antenna analyzer to the RCS-8V.

Why such a large bump?

Found it!  Cushcraft R5.

I picked up what looks like a multiband aluminum vertical of unknown manufacture.  There is a black plastic box near the base that houses a couple large toroids.  It is about 18 feet long, has two gamma matches and two hairpin matches and loading coils.  I seem to remember a common advert several years ago whose manufacturer featured a picture of the matching box with the toroids inside.  The PC board inside the box to which the toroids are mounted is dated 1991.  Anyone remember who that was?