Calrad 202M tube tuner, antenna?
- Thread starter notsofast
- Start date
mhardy6647
Lunatic Member
well - at least it's an unbalanced input 
So, yeah, try 75 ohm unbalanced (coax) first.
So, yeah, try 75 ohm unbalanced (coax) first.
notsofast
Active Member
There are only two screw connections laid out horizontally (side by side) on a small bakelite strip. ALSO it is a very old tuner, would an early '60's Japanese tuner likely be configured for a 75 ohm coax antenna connection??
mhardy6647
Lunatic Member
It's certainly possible. Often the "native" input on the tuners is 75 ohm, and they'd have a built-in balun to convert it to balanced 300 ohm twinlead (because that was what was mpst popular, long ago, for TV/FM "downlead").
If you have an antenna with 75 ohm coax downlead, and if you don't want to cut off the F-connector, get a female/female union for "F" connectors, an F connector, and another piece of coax with an F connector at one or at both ends. Hook one end of your "other piece of coax" to the union, and, of course, the other end of the union to the F-connector on your antenna coax. At the other end of your new "jumper", either cut off the F-connector or just dress the coax thus: strip off the outer jacket, cut (if need be) and twist the braided shield so that it can be inserted under one of the screw connectors (GND). Strip back a bit (say, 3/8 to 1/2 inch) of the center insulator (carefully) to expose the center (hot) conductor, and connnect that to the other screw connector. Most coax has a single-strand center conductor, so you need to be careful not to nick it when you strip the inner insulator, and don't twist it with too much vigor when you attach it to the tuner
Heck, maybe you can even buy a 75 ohm coax jumper with an F connector at one end, and two bare wires (or spade lugs) at the other!
PS - I am assuming you're in the US; if you're elsewhere, your standard coax connector probably won't be an "F" connector.
If you have an antenna with 75 ohm coax downlead, and if you don't want to cut off the F-connector, get a female/female union for "F" connectors, an F connector, and another piece of coax with an F connector at one or at both ends. Hook one end of your "other piece of coax" to the union, and, of course, the other end of the union to the F-connector on your antenna coax. At the other end of your new "jumper", either cut off the F-connector or just dress the coax thus: strip off the outer jacket, cut (if need be) and twist the braided shield so that it can be inserted under one of the screw connectors (GND). Strip back a bit (say, 3/8 to 1/2 inch) of the center insulator (carefully) to expose the center (hot) conductor, and connnect that to the other screw connector. Most coax has a single-strand center conductor, so you need to be careful not to nick it when you strip the inner insulator, and don't twist it with too much vigor when you attach it to the tuner
Heck, maybe you can even buy a 75 ohm coax jumper with an F connector at one end, and two bare wires (or spade lugs) at the other!
PS - I am assuming you're in the US; if you're elsewhere, your standard coax connector probably won't be an "F" connector.
notsofast
Active Member
Connecting 75ohm coax (shield to grnd lug, center copper to ant lug) did improve the reception. This tuners' antenna lugs did appear to be configured for 300ohm but it must have an internal transformer. Improved weak signals by no less than 35%, but when I put a splitter in the line for the Pio-780 it seems I lost 15% of what I had gained at the Calrad tuner. The Pioneer SX780 receiver has only center tune meter for fm (no signal strength meter). The splitter I'm using says -3db gain loss at each of it's two outputs, is there a better low loss 75ohm splitter available? Thanks for any replies
amptramp
Well-Known Member
The output ports on a splitter may not be all that well isolated. If the input goes to a tuned circuit (most tuners), the tuned circuit accepts the signal it is tuned to but acts as a short circuit away from the tuned frequency. This in turn may affect the other output. To test for this, connect two tuners to a splitter and set one tuner to a weak station. Tune the other tuner through this frequency and see what happens. In fact, the tuner you are not listening to may not have to be on as long as it is tuned by a variable cap or inductor, but it would have to be on for varicap tuning. Some cheap tuners used a grounded-grid stage with no tuning ahead of the RF amp and these show very broad tuning that would not affect anything else that much.
A coax switch or relay sized for 75 ohms might give you a better signal.
A coax switch or relay sized for 75 ohms might give you a better signal.
