Entries from June 2014 ↓

Estate Sales

Unless I know the people involved, I tend to avoid estate sales. I am particularly leary of estate sale items that show up on classified listings.

For instance, I recently found a Drake TR4C being offered as an estate sale item without power supply, as is, for $325.

There are several problems with this offer. First, is it worth $325? If it is in good working condition it certainly is worth $325. It may even be worth the additional $40 it will take to have it shipped. All this worth is based on it being a working transceiver in good condition.

It is being sold ‘as is’ without a power supply. To check it out the seller has no way of knowing what it is as. We have to assume that it is probably not working. Chances are very good that this orphaned radio got that way for good reason.

Hams are not given to retiring equipment that is working well. Should it be working well when retired as it is being replaced with a newer rig, the retired rig will end up being sold. If it is not worth selling, it may end up on a shelf, orphaned, with its power supply sold separately. The transceiver remains on the shelf until it is rediscovered when the ham passes on to the happy hunting ground.

After the surviving friends and relatives pick over the goodies he left behind, the remaining flotsum is readied for the ‘estate’ sale. Those items left after the first sale get listed on the classifieds.

After spending 30 years in a closet, idle and orphaned, the TR4C is most likely in even worse condition than when it was first abandonded there.

So is it really worth $325 plus shipping. Not until it is refurbished, provided with a power supply and microphone, and checked out for proper operation.

Its ‘as is’ value would not justify a $40 shipping charge.

50 Percent Off !!

Why is this offer only extended on stuff I don’t need?

I can’t save money by buying stuff I don’t need.

I can save money by ignoring the offer.

So when I see that offer I take 100 percent off.

I guess I am just a greedy old fart.

More Bazooka Dipoles

Nearly a year ago I invested in a Unidella trap antenna kit. It included two 40 meter traps, two end insulators, and a center insulator/balun. The resulting trap dipole ended up being somewhat narrow banded favoring the cw portion of 40 meters and the 75 meter ssb band.

The antenna seemed to work reasonably well on 75 and 40 meters but did not cover other bands as well as my home brew 80/40 trap dipole. That was not a problem as I had other antennas covering those other bands but I did want a 40 meter capability that would favor the entire 40 meter band.

So why not build another 40 meter bazooka, hang the traps off that antenna and add wire to cover 75 meters. The traps would not care that the 40 meter portion was a bazoola.

It also turns out that the bazooka does not care what coax you use to build the two quarter wave stubs as long as they are 40 meter quarter wave stubs, they will work. So I ended up using some surplus RG62 to build the quarter wave stubs.

Antenna Pulley System

The current problem is one padeye being used as a fulcrum for a halyard with too much weight on the halyard making it difficult for the rope to pass through the halyard fulcrum.

The heavy weighted halyard would pass through a properly configured pulley with roller. The pulley with roller would easily pass through the padeye fulcrum.

This works well but the pulley needs to be attached so that it does not slip on the line.

The bazooka modification has the 40 meter portion SWR best at 7.074. Need to take about 6 to 12 inches off each leg.

Now I have a 75/40 meter trap dipole that covers the entire 40 meter band with a 1.2:1 SWR and allows me to transmit on 75 meters as well.

Kenwood TS-120 repair

One of the more common problems with the TS-120 is loss of sensitivity on all bands due to damage to T1. There is a service bulletin out suggesting replacing T1. Trouble is the part is no longer available and there is little instruction as to how to go about the repair. There are hints suggesting it is easier to add the additional protection diodes to the foil side of the RF circuit board but little information detailing how to get to the foil side of the board.

Obviously the most direct way to access the foil side is to remove the RF circuit board completely. This requires removing the VFO and front panel along with all the knobs and band change gear. Be careful when removing the two screws that hold the band change gear shaft retainer. The two screws that require removal are recessed into cutout holes in the front panel. There are two other screws that are not recessed. Don’t disturb these two non-recessed screws. They are ground points for two resistors and a pot. Messing with these screws will destroy these components. While it is not impossible to remove the RF board, there is an easier way.

Flip the radio over and remove the IF board located under the RF board. There is a removable shield below the IF board. Removing the shield will give access to the foil side of the RF board. The RF board does not need to be removed.

Problems with T1 begin with static discharge or high power rf pickup at the antenna. The antenna input circuits consist of L1, L2, and T1. L1 and L2 are traps. T1 is an impedance matching transformer which has a nasty habit of allowing its primary to short to its secondary under very strong signal conditions.

T1 is very inconveniently located under the bandswitch shaft. Ohm it out to verify primary to secondary short. If shorted it must be removed from the RF board and repaired.

T1 repair is difficult but not impossible. Remove the shield and cupcore. Cut one side of the secondary winding and unwind it. Make sure the wire that is cut is the outside wire, the end of the winding. The secondary wining is the larger and outer winding composed of 70 turns of #30 wire. Using clear Krylon or similar laquer as glue apply a few drops to the surface of the remaining winding on the form. Allow the paint to become tacky and apply a thin strip of mylar around the winding to prevent future shorts between windings. The mylar may be cut from a ziplock bag. A 1/8th inch wide strip is more than adequate.

Once the mylar is stuck, rewind the wire onto the form trying to be as neat as possible. The re-winding may be shorted by one turn to allow enough wire to attach to the connector pin. Heat from the soldering iron will be enough to remove the insulation from the wire and make the solder connection to the terminal pin. Re-install the cup core and shield. Check for continuity and re-install to the RF circuit board.

Check the remaining diodes on the RF board to verify they are not open or shorted. Replace any as needed. Install the extra protection diodes and re-assemble the radio.