[peteivan]

I have been sidetracked from this project by several other projects. I restored a military R390A/UUR communications receiver for a customer. Also restored a Fisher model 500 mono tube type receiver, and a 1931 Dewald radio, including cabinet restoration. I also put together an amplified antenna kit sold by Ramsey. (For the AM broadcast band) It uses a shielded ferrite loop. The amp consists of a MPF 102 JFET feeding a 2N3904 emitter follower. I tried it on the R390A I was working on, tuned in a weak station at 1600 Khz. With a 30' wire streched out in the basement for an antenna, the station was barely readable-the signal being covered by noise from the CFL bulbs in the house. With the active antenna in the circuit, the interference almost completely ceased, the signal level jumped up by 20 Db, and the station was completely readable. I didn't like the cheap RCA jacks supplied with the kit. I used the plastic cabinet back on the control/power supply unit as a template to make a back made from brass on which I placed chassis mount BNC connectors at the same location where the RCA phono connectors were. (Don't forget to ground the brass plate to where one of the RCA connectors would have been grounded on the circuit board) The F connector on the remotely mounted antenna/amplifier unit was also replaced with a BNC connector. I didn't use the aluminum foil they suggested for the antenna shield. Thin copper sheeting is far easier to use, as it can be easily soldered, and is available at any hobby shop. (as are brass sheets in various thicknesses)
I plan to get back to the Philco 38-690 project soon. For the most part, the jukebox amp has been modified to work with the receiver chassis. I duplicated the Philco loudness compensation circuit on the jukebox amp chassis. This will probably require some tweaking of component values. The receiver/Amp combination is now ready for testing.
The manual for this amplified antenna kit can be downloaded from the
Ramsey website. It explains the theory of operation, but does not give you a schematic for obvious reasons.