What Do Hams Do?

On June 25, 2014, I had the honor of being invited to join a team put together by the Philippine amateur Radio Association, Inc. the national ham radio organization, now led by Ms. Thelma Pascua DU1IVT,  that would give a ham radio orientation seminar to some students of the University of the Philippines in Diliman, Quezon City.

I finished EE in 1977 and was glad to be back in the campus. But the real homecoming I was really  excited about was that of Ham Radio  since it has been 43 years since the last amateur radio activity in the Diliman Campus. Back then students (1971 operated CW and AM from their DU1UP ham shack in the 5th floor of the Engineering Building. A friend, Mario Quitoriano, ex DU1DFU told me, a lot students operated there were from non-engineering colleges. They taught each other the Morse code.I remember reading Dr. Edmundo Reyes  DU1OR's book, stating that  I read that the first campus ham radio station was established by an Australian EE student back in the 30s when the campus was still in Manila.   Dr. Reyes (who became PARA president multiple times) recounts that this Australian student Sol Mathhew Dakis was first secretary of the Philippine Amateur Radio Association which was headed by Leon Grove, its first president.
I thought I'd share some notes for that ham seminar. It is a question often asked us by many non-hams.

Many thanks to Professor Gene Cuaresma, DU1RNA University of the Philippines Los Banos.

Summer 2014 DU1 Swapmeet!

Summer 2014 DU1 Swapmeet!

Souvenir Photo late afternoon, just before the end of the swapmeet (best lighting for photography)

DU1DT Dick's new 2kw tuner bought in the last few minutes of the swapmeet for a good price! 

DU1FV 23cm YAGI from a CDR-King tv antenna

DU1FV 23cm YAGI from a CDR-King tv antenna 

Now that you have got a 23cm radio, you need an antenna. 

Unfortunately, they are quite rare and if available sometimes expensive.  Here are some photos of a prototype yagi I made from parts off a P200 HDTV antenna from CDR-King.

Below is the original P200.00 HDTV antenna. It is a relatively compact antenna.

There is a lot of element (~1/4 inch Al rod) material so it is perfect for protoyping.

We proceed to strip the original elements from the boom,

The design of this antenna is based on the method of perturbation.

The following steps are followed:

0. Mount the boom securely.
1. A driven element (DE) style is selected.  In this case I choose a double bazooka style of element.
I made it out of 3/8 copper tube from a ref supply house.I split the center and inserted the foam insulator with center conductor from a piece of 50 ohm foam type coax.  To make it a bazooka, I soldered the center conductor by flaring the strands so they touch the rim of the copper tube at the ends. See picture below.



2. The DE is cut so that it is resonant at about the target frequency and is tuned as a simple dipole directly fed by coax via suitable connectors.




 It has to be mounted on the boom when measuring swr.
It took me three tries before I got an acceptable reading, about 1: 1.8 to 2.0 I used a vhf-uhf cross needle swr meter by Daiwa. It is not calibrated for 1200MHz But it reads 1200mHz energy quite well (too well  in fact: ten watts wold read 25w) and is ok for relative measurements for swr.
 3. A field strength meter (FSM) is devised from a common analog volt ohm meter. If you tx with your portable with rubber duck antenna next to it there should be some reading while it is in the AC posiition.  It does not have to calibrated because it is only use for relative measurement.
4. A wood chopstick is used as a temporary element support and one element of the orig tv antenna is cut to about textbook length of a dipole plus maybe ten percent. Use masking tape to attach the element to the chopstick.
5. Position your FSM along the book till you get a reading when you drive the DE.  Then slowly position the first parasitic element on the chopstick in between the FSM and the DE. Obeserve if signal goes up or down as the field is "perturbed" by the proximity of the parasitic.  Compare the reading with another one taken with this time the parasitic in the "back" of the DE (which puts the DE in between the FSM and the parasitic.  since we have cut roughly long w the behacior we are looking for is tha of a reflector.
6. Generally if the signal reading goes up when the parasitic is between the FSM and DE, the parasitic is "short" and behaves more like a director.  If on the other hand, the signal decreases, it is acting like a reflector effectively shielding the FSM from the DE.  If this is the case, yo will generally find that if you put in the back of the DE, the FSM will read slight ly higher compared to one taken with the parasitic removed from the vicinity of the DE.  You will now have a feel if the parasitic is long or short.
7. Make another parasitic, one slightly shorter maybe by one half mm. Try to replace the old parasitic with the new one.  If it sit still behave as a reflector , that is good. If it is a better reflector (measure FSM) let it be the new reflector.  You can now grind down the first parasitic you made to make it shorter by half an mm. then replace the mounted one with the newly shortened one and see the FSM reading.  By now you should get the drift.
8.  There will come a point that as you shorten the parasitic it will become a "director" and you can confirm this by placing it in between the DE and the FSM the signal should go up dramatically.
9. The same process of slowly cutting and grinding down the succeeding parasitics will yield a quite decent antenna. as long as you are careful with FSM relative measurements.  also check the swr now and then.

Remember to always compare reading BEFORE and AFTER a CHANGE.  And follow the EXPERIMENTORS CREED: " CHANGE ONE THING AT A TIME"

10. At one point you may even feel that your driven element is too long or short as swr will vary as you add elements.  In my prototype I did have to change the DE length just once after adding the fourth parasitic and the swr kick back to acceptable level.







    This in a nutshell, is the process of perturbation. Unlike blindly following published design specs, it "automatically" takes in to account element diameter, height above boom, diameter of boom etc.  It is a bit like analog computing.  The principle is not my own. I first read about it in a ham magazine during the 80s.  I am not sure but it was probably QST and the author did it for a uhf beam.

Notes

    There are existing evenly spaced holes corresponding to element spacing of the HDTV antenna. I decided to stick the original spacings and do element length tuning only, so I can use the existing holes.  There might be more optimum spacings but I did not want to weaken the boom too much by drilling more holes through it.  Since this is a cheap HDTV antenna, the boom is not too sturdy.

Enhancements

     This is a prototype and can stand some improvement like enclosing the entire driven element in a waterproof radome of some sort, but I will leave it up to you to think of enhancements.

73 Ramon DU1FV

Happy Fourth of July to our brother Americans!

Happy Fourth of July to our brother Americans and that goes double for my cousins in the Land of the Free and the Home of the Brave! Independence Day: As Filipinos, we should be proud to be the first in Asia perhaps in the world to go from a dictatorship to a mass based democracy with the People Power revolution so well emulated by many peoples in Poland, Germany and others. We belittle ourselves if we do not recognize that we are also the first to form a national government in what was a colony or under the hegemony of a Western power. We beat India, Indonesia Malaysia, even China's Dr. Sun Yat Sen's Republic of China. It is a fact that wars are won and lost, but the first spark of national identity was ignited by Andres Bonifacio in his Haring Bayan government. Unless I am mistaken the Americans have not yet won the Revolutionary War on July 4. So they do not celebrate "Independence" but most importantly the "Declaration" thereof!

Make yourself some Health Rice!

My First Heathkit Oscilloscope

My First Heathkit Oscilloscope

"Naku, itong si Ramon, kung anu-ano pinabibili sa Ate Josie niya. At para saan naman iyan? Sa hobby lang?" (translation: Darn this Ramon, what is all these stuff that you keep pestering your cousin Josie in London to buy? All this for just a hobby?") So complained my elder cousin about the first oscilloscope I asked my cousin working in London to buy for me (In fairness, even as he compalined to me, he did give me some instructions to aid me in clearing the importation). I was still in college. It was still the 70's then and importing things into the country was more restrictive than in it is today. Even for stuff like this you had to go through hoops and mazes with then Central Bank (with it's import regulations) and Customs, It was a nightmare, I recall. But was it worth it? Well one year later, it was the same elder cousin who found himself in a bind because he needed somebody to repair some "exotic" electronic geophysical measurement equipment somewhere in San Carlos University in Cebu. Days after I was on my first flight to Cebu, with my heathkit scope in tow. The faulty gear was some resistivity equipment which used a dc to dc converter to provide high voltage that you applied to the earth and while measuring voltage on a another set of probes. I was able to fix it and it was on a later talk with my cousin that he himself reminded me of the scolding he gave me a year ago and he then admitted "mayroon pakinabang pala!" (translation: It turns out the scope was not a bad idea at all). I felt really good that day! After I graduated college, I was recruited by my cousin for his new geophyscal instrumentation division which exposed me to radio telemetry, seismography (yes- earthquake instrumentation!), basic digital computing (our cpu had magnetic memory and paper tape storage!) in several training sessions in JA.
I sometimes ask myself: "what if I never bought my heathkit scope?"

Calibrating the Kenwood TR-9130 with your HF rig

Calibrating the Kenwood TR-9130 with your HF rig

How to calibrate the frequency reference of the Kenwood TR-9130 using your HF rig and the Internet (yes, you read it right, the Internet). The Kenwood Service manual requires that a frequency counter  good for 130Mhz plus be used to calibrate the PLL of the Kenwood TR-9130. I don't have one, but I do have the trusty TS-850S, so I tried to figure out a way to adjust the vhf all mode transceiver using the HF rig. Please read these and follow instructions in its entirety. There are two frequency determining sections of this rig. One is the carrier unit and the next is the PLL 14 mhz oscillator (which generate the 0 to 9.9khz spacing of the PLL). Measuring the frequency of a carrier with an HF receiver can be tricky.  So I deliberately tuned the receiver 400 Hz away so there would be a beat note if I monitor the signal whose frequency I was interested in measuring.  I can hear a beat note  but how do I know it is precisely 400 Hz? That is where the internet comes in. You can download or hear samples of 400Hz on many sites. If you listen simultaneously to the internet sample and the sound coming from the hf speaker you will note that the beat note can be zeroed out as the two frequency comes close and eventaully synchronize. You will note this "motor-boating effect when you either tune the hf away or near the signal or vary the frequency of the signal under test by adjusting a capacitance or resistance (in case of varactor circuits). Part 1 We use the hf as receiver and monitor the carrier unit output. Attach a short piece of wire (to act as probe) to the center conductor of a coax connected to the HF receiver. Dangle this wire in the vicinity of the carrier unit. You should receive a strong signal. Offset the receiver by exactly 400 Hz. Surf the internet and google 400 hz tone and listen to the sample. The WWW sample should zero beat with the tone coming from your hf speaker. You should adjust the carrier unit, using the table below from the service manual below (frequencies are actual carrier output, you must tune the receiver 400hz away) :  Mode  tx or rx  adjust  frequency  USB  rx  TC3  10.6935 MHz  CW  tx  TC2  10.6943 MHz  CW  rx  check  10.6935 MHz LSB   rx  TC1  10.6965 MHz Adjust the trimmers you while listening the beat note between the WWW 400 Hz sample and the sound coming from the hf speaker. You should be able to sync within a few Hz.  After finishing the Carrier Unit  adjustment. what remains is the main PLL. The service manual require a 130 + mhz frequency counter which I do not have, so we devised a workaround.   Part 2 After the CAR unit you must adjust the PLL 14 MHz oscillator. Instead of acting as a receiver. the hf will now be use as a signal source. We shall transmit on ten meters while we monitor the 5th harmonic with the TR-9130. Set the TR-9130 at 144.9999 USB. Your hf should be set to 10 meters, AM or CW with this frequency: (144.9999 +.0004)/5=29.00006MHz .  The ".0004 is" the 400hz offset.  What this mathematical equation is trying to say is that in order to hear a 400 hz beat note on the tr-9130 speaker, it has to receive a 144.9999 + 400Hz (= 145.0003 MHz) signal assuming the receiver vfo is set to 144.9999 .    And 145.0003  would be the fifth harmonic of a 29.00006 Mhz signal, which our hf transceiver can easily produce so we set the hf to this frequency. Put a short piece of wire at the TR-9130 antenna input as a rx antenna. Connect hf to a dummy load. While transmitting a low level carrier, You will now adjust TC1 for zero beat between the TR-9130 speaker tone and the WWW 400hz sample tone played back on your computer's speaker. Tune HF rig to (145.0000 +.0004)/5=29.00008MHz and adjust VR1 for zero beat, similarly. On the PLL board, the 14 mhz oscillator alignment is pretty tricky. you will know you have done everything right if there is a normal change in pitch of a received carrier as you go through 100Hz steps, particulalry from say "4.999.9 to 5.000.0 while on sideband receive. If you notice a jump in pitch greater than with an expected 100Hz vfo change, you have not done the adjustment right. Proper setting of TC1 and VR1 apparently insures linearity of the 14 mhz VCO which controls the 100Hz steps.  Do not attempt this before understanding the underlying principle of your Kenwood TR-9130 PLL system. Do not attempt this if you are unqualified or feel nervous. It is possible your tool may slip and damage the radio. Extreme caution must be exercised as adjustments are done with the radio turned on.  73 DU1FV