Field Strength Meter Circuit Diagram
Save those transformers from old rotor control units. You'll find uses for them. One is a transistor power supply- With a bridge rectifier, you can get 30 volts plus at more than 30 ma. plus. , . . K0VQY
UHF TV is gone for a lot of areas. There are UHF converters (and probably) old TV boosters also. A majority of these contain a transformer that delivers 6-3 volts and 125 volts at 30 ma-, that is isolated from the line. Preamps, bias supplies, small set supply and a load of test gear you can dream up can be built around this. . , , K^VQY
Erml Carp W3JXT Montgomery ville, Pennsylvania
Erml Carp W3JXT Montgomery ville, Pennsylvania
(for a Porsche
A couple Oi years ago I was intrigued by the description of how to buy a Porsche in Germany which appeared in an editorial by Wayne Green, The story influenced me to do the same.
After surmounting the minor obstacle of a boss who didn't want to giva me time off for European trip by convincing him to come along as my co-pilot, all went smoothly. The car was waiting for me at the factory and it was a dream to drive. We traveled 4500 miles through Europe, enjoying every minute of it.
Once the car was home, I started looking at it critically with the idea of putting in a mobile rig, Porsche owners, Volkswagen owners, and others who have to match wits with the restricted room problem may benefit from my solution. I fitted everything into a package 4" high by 13Mi" wide and with a panel only 2%" high to stick out from under the dashboard.
The receiver used was a Bendix all-transistor broadcast set made especially for Volkswagens. I had a Tfcanseon six meter unit which was easily modified to tit in the new package, giving me a crystal controlled converter and transmitter combination. I had to lower all of the Transcon tuning controls and change the plate coil to a horizontal position to get it into the flat case. The vibrator power supply was mounted up front in the luggage compartment and relay controlled, I installed the trans is tor-condenser combination shown in Fig. 1 to suppress any arcs across the contact points. Perhaps I'm a worry-wart, but I get nervous when gas stations spill gas into the luggage compartment while trying to get it into the six inch wide racing spout on the gas tank.
An SWR unit was incorporated using a Lafayette AM tuning meter TM12, The plastic case was carefully opened and the resistor removed, leaving me with a 50 ua movement. 1 built the rest of it using the Heath SWR for a model.
I used 1 l(5th inch aluminum for the cabinet, bending each side and using sheet metal screws to fasten all the sections together. With the addition of flat bottom and top plates I had a rigid case. Holes in the plates provide ventilation.
The set mounted in the car easily. A small angle bracket on each end fastened to the bottom of the dash and a quarter inch bolt secured the back end to a bracket attached to the car. I used power plugs on the cables so ! could take the rig out whenever I wanted with just a couple minutes work.
This is no place to go into ecstasy over the joys of mobile hamming, so suffice it to say the rig works fine and I wouldn't be without it. The Porsche is fabulous and I pity all you poor chaps who haven't had a chance to try the breed- . . . W3JXT
Apparently EtCO is trying to outdo everyone e!se In battery eliminator design. This new one has everything you can imagine. 1 \ is fi tered w iih 5000 tnfd for use with transistor radios and will handle the currents necessary to charge six or twelve volt batteries. It has rwo ranges, 0-8 vdc and 0-i 6 vdcn and the meters switch as you select the range desired. $43.95 in kit form and $52.95 ready to go. Load: 10 amps continuous and 20 amps intermittent on low range, 6 amps continuous and 10 amps intermittent on high. L1CO will respond with full particulars on this or any other
^ I 1 it IT
EICO product if you but let them know of your interest. El CO. 33-00 Northern Blvd.. L. I. C. 1, N. Y.
7035 LAUREL CANYON BLVD.,
NORTH HOLLYWOOD, CALIF i. MICHIGAN AVE., H
CHICAGO, ILLINOIS ■
COLLINS XMTR. & RCVR, Collins RT-91/ARC-2, 2-6 mc AM 75
waff transmitter and receiver. Late modei aircraft, Rcvr. has 3 RF stages, ultrasensitive- 20 tubes, VFO controlled unit with bui It in autotune and 24 vdc dynamotor. Hos7QE PTO and 100 Kc crystal calibrator, Pr. 1625 final and pr 1625 modulators. With schematic.^ ^¿O 95 GOOD, USED
1215 mc transmitter & rcvr. Consists of superhet rcvr & pulse xmtr, for operation on 950- 1 330 mc band. Xrnfrr. 2 1/2 ivott output CW frequency 1215-1233 mc. Rcvr. 10QDBM 2300-2465mcsup-
erhet. Cavity contains local osc., xtl mixer, I 2C42, I 2C46 tubes, Veeder counter. With tubes ^ Q
100 watt xmtr* idea! for domestic use as well as export marine and mobile! Freq. 200- 12,500 kc. with proper tuning unit CW or MCW> Excel lent Cond?§2 9J PE-73 OYNAMOTOR for above. Input-24 v. Output-1000 ?'300 ma. w/filtering base* Excel. Cond, ^ 7 2r TUNING UNIT for 80375.^.^/05
ANTENNA RELAY - BC-442 complete with 10 RF meter & 50 mmf capacitor @ 5 KV. New Cond, $
JAN 717A TUBE - Excel- Sub for 6SK7
THORDARSON POWER XFRMR * 49690 PRIMARY: Tapped 105 - 125 v 60cycle SECONDARY: 1050 v,c.t. @ 100 ma, (2) 6, 3v ® 3 Amp- (1)6,3v @ 2 Amp. (t) 5v @ 4 Amp. NEWCand. With Schematic » —
MARINE SPECIAL — 12 V. 75 Amp heavy duty battery. New cond
COMMAND SETS T~7 T-T8/ARC5 2, l-3mc New co BC458xmtr. 5.3-7mc New cond.5^' 8C453 rcvr* 190-550kc Excl____^ 9 *
The e hief
A little rig comes in handy now and then.
It may be used to let the fellows know what happened to you when the smoke started pouring out of the big rig, or it may Vie just for having a little fun down in the Novice bands, "his Little Thief steals its power from your receiver, thereby reducing its cost and weight to a minimum.
Your receiver probably has a socket on the back for powering a calibrator, converter, Q-multiplierf etc., so why not plug in a small one-tube transmitter? This won't overload the receiver because the transmitter doesn't draw any more power than the receiver and is only used when the receiver is on standby.
Step one is to get out the manual on your receiver and see how they have the accessory socket wired. Ail receivers have at least the filament, ground and B-plus available here, You will need some method of switching the B-pIus from receiver to transmitter. If your receiver does not have a double-throw switch built in, which it probably lias not, you have a choice of either substituting one for the present standby switch or else mounting a suitable switch on the transmitter and letting it perform the duty. This is probably the best bet • . * and simplest.
Many receivers have the B-pIus go through a jumper on the accessory plug. If you have one like this then your problems are few, All you have to do is remove the jumper and run the wires to the new switch and use that in stead of the one on the receiver. If the manufacturer has been remiss you will have to do the work and break the B-plus lead as it comes from the standby switch in the receiver and run it to two empty terminals on the socket.
A single crystal oscillator stage is used with a pi-network tank circuit This will match into random length antennas and give you good harmonic rejection- Both crystal and coil can be changed easily for hand changes. A doublepole double-throw switch is used for transmit-receive so you can switch both the B-plus and antenna circuits simultaneously. This gives you one switch operation and you don't have to use any antenna relays.
A small pilot lamp could be used in place of the meter for tuning, but with the low price on meters this doesn't make much sense , , , and besides a meter is a lot easier to read. If you don't have a meter of the right range it is simple to wind up a small shunt and use any meter of lesser range.
CI tunes the tank, C2 determines the loading. Tune CI for a resonant dip on the meter and
then tune 02 for best loading, I find that a small field strength meter is very handy for getting the best loading. With experience you will see how the plate meter responds to loading and be able to tune by it alone, C2 will affect the tuning of CI a bit, as you will see. On 40 meter C2 has a greater effect on tuning and you may have to try several different settings to determine the best output. For best stability of the keyed note you should back off the maximum dip just a bit with CI. Experience is a fint- teacher and this little rig will be quite an experience.
W ith a 65 foot antenna and proper loading on both 40 and 80 meters 1 found that 12 ma plate current gave me the best results.
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