Send For Rohn Tower Handbook

—ONLY $] 00 postpaid (special to readers of this magazine). Nearest ; source of supply sent on request. Representatives world-wide to serve you. Write ; todav to:

ROHN Manufacturing Co.

Rohn Tower Peoria

Peoria, Illinois

Peoria, Illinois

* World's Largest EXCL Lisi VE Manufacturer of Towers; designers, engineers, and instalUrs of complete communication, toner systems."

move the bfo coil assembly by removing four screws (don't lose them!) and all bypass capacitors, Check the bypasses with a neon bulb and a 150 volt source to make certain they aren't leaky or open. A good one will let the bulb blink once, but no more- Any glow, or lack of the initial blink, indicates a bad bypass.

We've saved the hardest part, removing the capacitor gang, till last. Remove the tuning dial. Behind it, vou will find four small screws on the panel. Loosen them but do not remove them vet. Now check the connections to the capacitors. The rf and mixer connections can be removed at the capacitor, but you want to retain as much of the original oscillator wiring as possible. On mine, u No. 12 wire ran down to a feedthrough on the chassis, and disconnecting it from the feedthrough let me lift the w hole unit free. When yon are certain you have the wires under control, remove the four screws and lift the capacitor free.

Next step—and if it's late in the evening wait till tomorrow because it's really the hardest part of the whole job—is to drill and shape all the holes in the chassis. The rear-skirt layout (Fig. 2) and the panel template (Fig, 3) should be of help here. After all holes are drilled or punched, smooth off all burrs and mount the tube sockets.

Now the wiring begins, Run the filament line first. After it is complete to all sockets, add the 6AQ5 output stage components, including the audio output transformer. Now, wire in the power supply in the space between the output transformer and the 6AQ5 socket (and as you do this, you will understand why this order was prescribed—the ft A Q5 socket is inaccessible after the power supply is installed!).

W2ewl Special
Tuning dial, full size tracing

After checking to see that all filaments light properly, remove tubes and disconnect uc power (short out the filter capacitors, too, for safety). Install the "W2EWL" transformer and wire all B+ lines, dressing the wires and decoupling components as close to the chassis as possible. Now you can finish up the 12AX7 audio stage, and reinsert the two audio tubes for a checkout. If all is well so far, you should he able to get a loud hum by touching the input grid of the 12AX7 with a screwdriver.

At this stage, add the volume control and speaker switch on the front panel and connect them in. You now have a fine audio amplifier ready for service; the next few steps will turn it into a receiver.

Next step is to wire the 6BU8 stage, and insert the last if transformer in its chassis hole and connect it The Makino limiter/AM detector is hooked up separately on a five-point tie strip and installed after this wiring is completed.

The other if transformers can be mounted now; hold them in place with 4-40 screws and nuts through the mounting lips, and connect by soldering directly to the "sockets"' on the bottoms of the coils. Install the rf gain control the avc switch, and the function switch on the front panel, and wire the if stages and the controls into the circuit.

The avc components can be added conveniently at this stage also. They fasten to a tie point on the bottom of the chassis, to the tube socket, and to the avc switch.

All that remains is the front-end wiring. Make all possible connections to the tube sockets. Connect generous lengths of insulated wire to all tube-socket p:ns which have any connections to be made to the coil assembly or capacitor, since you won't be able to gel to them later.

Now angle the tuning capacitor into position. Before installing it permanently, you 11 probably want to add a dial as 1 did—just trace olf the calibration from the original dial plate, except that the old 200 mark becomes O' on the new dial and you go up from there, so that the dial reads from 0 to 350. I used "letra-set" lettering and copied the final tracing with an office-copy mach'ne, then glued the copy to drafting board and forced the board into place on the threaded hub of the timing capacitor.

The hairline indicator behind the viewing hole in the front panel was made by scratching a line on a piece of Incite. The whole works is held in place by masking tape against the inside of the chassis, and a No- 17 bulb across

Antenne Halo Metres

6-10-11-15-20 or 40 METERS

Cush Craft's continuing research produces another first -THE SQUARE HALO, Squalo is a full half wave, horizontally polarized, omnidirectional antenna. Outstanding all around performance is achieved through a 360'' pattern with no deep nulls. Full size and cam-pact dimensions provide a low Q for broad band coverage. Direct 52 ohm Reddi Match feed gives an SWR of 1-5-1 or less from 50 to 51 Mc,

The 6 and 1 1 meter Squalos are packaged complete with rubber suction cups for car top mounting and a horizontal support for mast or tower mounting. The 10-15-20 and 40 meter Squalos are designed for mast or tower mounting where space does not allow for larger antennas. Squalo is ideal for net control, monitoring, or general ham coverage.

Whether you are a beginner, apartment dweller, or serious DX man the space saver Squalo is for you. You can buy one for each band and build a Squalo Tree!

Was this article helpful?

0 0

Post a comment