Saturday, April 30, 2011

Chili Fly-In at Massey 2011

The highlight at the 2011 Chili Fly In was seeing the 1911 Curtis flying.

This reproduction was built from original drawings and to celebrate 100 years of Naval Aviation.

More info on the plane is at

More info on Massey at

More Pix at

ATS-4a field tested with KI6J End Fed Matcher

ATS-4a in use in VA at portable location

KI6J Matcher with #22 teflon 1/2 wave for 20M

KI6J Matcher 'hooked up' on 20M

Put both the ATS-4a and the KI6J matcher on a field test at the portable location in VA.  The half wave wire was indoors on the 2nd floor and contact was made with an F8 with a 579 report!  The LED worked on the matcher to tune the antenna and several US contacts were also made.  The power supply was a 4.5 AH Gel Cell.  The headphones were Skull Candy ear buds and the Vibroplex Code Warrior Jr. works without the plastic paddles too.

Thursday, April 28, 2011

NorCal S1-S9 Xtal Socket Mod

Original 10Mhz Xtal in Socket

Socket Added

A left over piece of the LCD socket from the Code Reader is the same pin spacing as the xtal if you cut off the 'middle' pin.  After soldering the socket in position '3' now becomes a socket and I tried testing HC-29 and HC-6 crystals for testing.

Wednesday, April 20, 2011

Electrovoice Aristocrat

Here is a 1952 Electrovoice Aristocrat Corner speaker with a Jensen 12" K-210 driver.

Catalog sheet for Aristocrat

Catalog sheet for Jensen K-210

If you are interested in this contact me

Bose 301 Series III

Bose 301 Series '91-'96

Not sure about the 'bracket'?

Sunday, April 17, 2011

KI6J End Fed Matcher in Box

KI6J in plastic box

Matcher with Lid and 5000 Ohm 'antenna'

Got the Dremel and cut some holes in the Rat Shack box to mount the KI6J End Fed Matcher in.  The 5000 ohm resistor will simulate a half wave end fed for testing.  The switch will switch the bridge circuit and LED in/out for tuning with the capacitor.  The LED will dim when the bridge is balanced and the match is close to 50 ohms.  Then throw the switch to xmit without the bridge.  A previous post has more info on this kit and a schematic.

Saturday, April 16, 2011

More Drake 2B Fun

Drake 2B

Pretty good copper!
14 Mhz computer crystal for 20M

Glow of tubes.

Before putting the tube tester away for the season.  I tested all the tubes in the 2B.  You can see the Hayseed Hamfest, the DigiKey computer crystal replacement for the 20M crystal that failed,  it is soldered to the base of the original crystal.

Friday, April 15, 2011

Last of the C-4 Corvette Wheels and Khumo Victor Racers

17" Sawblades

Still lots of tread for AutoX tire

275 40 ZR17

Rim Width 10? Tape is on ground

Saturday, April 9, 2011

TR-4 Crystal Filter

TR-4 Crystal filter (the Non -X) is dead on this radio and I thought it would be 'interesting' to open it up and see if it could be repaired inexpensively.  I ordered a set of 9mhz crystals from DigiKey for about 50 cents each and though it would be fun to experiment.

Testing Crystals

Rewinding a transformer

Bottom of filters in TR-4

Another View from Bottom

Filters out of radio in holder

From the top

Some of the crystals are bad

Ready to try and schematic

The filter now works but only sort of and it is not usable but it was a good learning experience.  The passband shape is not quite wide enough it sounds like a 1.6 khz filter, and it is not enough different from the other to really provide both sidebands with the Drake scheme of switching.  

Crystals used were a handful of unselected 50 cent crystals from Digi Key.  I made no attempt to characterize them.  

Opening the filter box required enough heat that all of the solder inside the box melted and this meant that the original crystal containers came unsoldered.  One cover even fell off when I got the box opened.  I used a 1500 heat gun and when the solder starting to melt I sucked it up with the Hakko 808 desoldering irom.  Massive amounts of solder wick and a LARGE iron will also work I am told.  

Crystals were tested using the old Heathkit IG-102 and watching the sinewave on the scope.  When the crystal resonates it causes a major decrease in the sine wave that can be seen.  Some of the crystals did this and some did not.  I really don't even know what frequency the originals were as they were unmarked and I do not have any documentation on this type of filter.  I assumed maybe incorrectly that they would use 9mhz crystals and 'pull' them a bit for either the USB filter or the LSB filter to give the proper shapes with the filter circuit and caps and coils.  

I suspect that either the crystals are not really 9mhz and maybe be a bit higher or lower.  The working filter which is marked 'U' has a peak response on the low side of 9Mhz so the 'other' one would need to be a bit higher to give the two passband shapes.  

The other thing that was interesting is that by using the RF Gen and a receiver you can do a crude 'sweep' to determine the filter shape.  

Using the working filter I plotted my 1kc measurement points and actually came up with something that looks like a filter curve.

Crude plot of working filter 

Another item of interest is that the insertion loss can be roughly determined using this method.  

This simple test set up using the antique RF gen showed that the insertion loss of the working filter was somewhere in the 5db or less range.

I used a piece of coax with a RCA connector on the end and fed it to an unused port on my antenna switch (not that much isolation).  This acts as an attenuator to avoid damaging the radio.  The RCA connector tip is used as a probe and the shield was grounded with a short clip lead.  Putting the probe on the input to the filter and tuning the generator (difficult with the antique) for max reading on the radio adj. the gen to provide a 20db over S9 signal.  Then measure the output at your different frequencies.  Using a spreadsheet program you can plot the curve and see what it looks like.  

My repaired filter has about a 20db insertion loss compared to less than 5 for the working original and the peak response is not quite a khz higher than the original.  

For extra fun I tried some 300pf caps in place of the 82pf caps and that did not seem to make much difference in frequency response.  

Not sure what I will try next but am hoping to build or repair a filter for this old TR-4.  Yes I know you can buy an INRAD and they do have great products.

Tested the old filters and the one spare using the signal gen and watching for min sig on the scope.  The three good ones left from the original set tested at 8.993.0 and and the Digikey  spare tests at 8.999.8.

The filter that is bad is marked as 2100L(SB) and the INRAD page lists their replacement filter with this data

2500 Hz 9000.0 kHz LSB 8-pole crystal filter

Bandwidth2500 Hz
Center Frequency9000.0 kHz
Zin/Zout1000 ohms
Typical Insertion Loss< 6 dB
Ultimate Rejection> 80 dB
Typical Carrier Rejection30 dB
Physical DimensionsSL case, same as OEM

Common design freqs for LSB and USB are 9.0015 and 8.9985 Mhz and the Center Freq of the filter pair really needs to be at these values.  

Wednesday, April 6, 2011

Heathkit IG-102 RF Signal Generator

While troubleshooting the TR-4 filters I thought it would be useful to see if this old Signal Generator still worked.  This is one of the pieces from Bill's old heathkit test gear.  I took the cover off to dust it off and check it out.  I sparyed some DeoxITD5 on the pots and switches.  The bandswitch felt 'locked' so I took the knob off and turned it with a wrench and it loosened right up so it was powered up and seemed to work once all the swithes and pots were 'exercised' a bit.

Heathkit IG-102 

Top showing 12AT7 and 6AN6 both original tubes marked Mullard and Heath

Bottom showing variable cap and coils

I looked at the output on my scope and it looked 'OK' to use for a lot of test and repair purposes.  I hooked up the two Drake TR-4 filters and could see the one that worked passed a signal about 3-4 DB down from the input signal when the generator was tuned to the filter frequency and the 'bad' filter would not pass a signal at all.  With the frequency counter and the scope one could plot the response if the filter was terminated 'properly' .

Drake TR-4 Crystal Filters

Drake TR-4 'Blue' Filters removed

Filters from Bottom of TR-4

Filters removed from radio

Measurement of Tedford SSB 9M 2100 U
Model 7970 Crystal Filter from TR-4
(the working filter)

Test conditions 
Heathkit IG-102 set to read 20 over 
Receiver FT-1000MkV

Rx F was set and Signal Gen was tuned for max meter reading on various F's

9.006.00   less than S1
9.002.00   less than S1
9.001.00   S8
9.00.00    S9
8.999.00   10 OVER
8.998.75   15 over
8.998.00   15 over
8.997.00   10 over
8.996.00   10 over
8.995.00   S9
8.994.00   S2


Monday, April 4, 2011

Drake R-4b Calibrator power supply

Top C190 Bottom C192 originals 

The calibrator in the R4b was sounding very raspy until it had been on for a few min.  (maybe 10 min) and then it worked normally.  I decided to order some more cap with the recent DigiKey order and today I replaced C190 with a 25V 220uf Digikey # 4035PHCT-ND and C192 with a 16V 1000uf DigiKey # P13119-ND and the Calibrator worked right away and sounded good.

I tested both of the caps on the Heath C-3 tester and the 1000uf was definitely leaky and would not provide a good null on the bridge.  The 200uf 6V original provided a good null at about 150uf but the min leakage test on the C3 is 25V and it definitely fails that which is probably normal for a 6V rated part.

The 1000uf is under the power transformer and it was not too difficult to get to and is the probable real fix.  The other cap is on the Cal board and I removed the 2 screws holding the board to the chassis and then the cap was readily accessible .

Timewave DSP

Timewave DSP-9 and 599zx

Received the correct TDA-2003 audio IC and some electrolytics for the DSP-9 today and tested it out.  Sounds like new with some new filter and coupling caps.  Will be great for some of the smaller rigs.  I used Digikey # 497-2161-5-ND  which is TDA-2003H.  The H means horizontal and it is actually vertical mount but this just means you have to bend the leads.  I put the leads in the board and bent the whole IC up bending all the leads at once.  This is not a big deal.  I also changed C38, C28 the large output coupling cap and the power supply filter.  Both of these were showing some leakage on the Heath C-3 Cap tester.  I also changed the input coupling cap to the IC and a couple of other 10uf in the audio amp circuit and two other 10uf coupling caps.  The two large caps tested a bit leaky on the tester the smaller ones seemed to test ok but I changed the obvious audio coupling caps anyway.  Sound like new now.  I like the 599zx better but the -9 does a very good job for the features that it does have.  Service is still available but it would have been $70 for the factory to change the audio IC.