Recently there has been interest on the repeater reflectors in the DB-4048 VHF notch duplexer for ham application.
This is something of interest to myself, since I currently have a ‘problem’ set on the bench myself.
Thanks to Gary K2UQ, I now have some old documents from DB Products on conversion of these cans to ham application suitable for 600 KHz splits.
Evidently some guys were modifying the less desirable six can bandpass ‘base duplexer’ (3 MHz split) DB-4046 by removing one pickup loop on each cavity, changing loops on the TX side for longer ones and constructing a new harness.
Here is the factory spec on DB-4046:
db-4046 base duplexer bandpass
Here are the specs on the factory stock individual band pass cavities:
Here are the specs on the factory stock individual notch cavities
Here are the conversions docs from Gary:
The DB-4048 factory stock duplexer came as a six can set of notch cavities. Ratings are about 70 dB of isolation. The TX leg notches the RX freq and the RX side notches the TX freq. This just isn’t 80-85 dB for current solid state PA’s. Evidently these cans were brought out around 1975 because the ARRL did a product review of them in QST June 1975 (I’m looking for a copy of this BTW). I imagine with a tube PA back then, these were more usable specs.
Evidently the modifications change the harness lengths for ¼ wavelength ham frequencies and also add on some notch stubs for additional rejection. I personally just got these conversion documents and haven’t had time to look them over closely or implement any of the changes to my stock set of DB-4048.
BTW, If anyone has the original DB-4048 specification out of a catalog, I’d sure like a copy.
Thanks to all!
73’s
Ralph W4XE
Email at [email protected]
http://www.qsl.net/w4xe/rpttech/rpttech.htm
Page created 1/5/04
