|
This page is to be developed with Frequently Asked Questions |
|
|
| Q There is a lot background noise
on the received signals and it is more noticeable as dusk/evening approaches.
Quite a few stations seem to be too strong for the receiver. Why?
A Leaky grid detectors (as used in the Paraset) are very easily overloaded. This will show up as background "mush" and breakthrough from some broadcast stations. You most certainly will not be getting the best from the receiver. The answer is to reduce the coupling from the antenna to the receiver. On this web site look at Top Tip No. 2 this explains how to do this effectively. Q The off load voltage of the D.C. to D.C. power supply seems very high off load...approaching 400v Why is this and is it normal? A The off load voltage will be around 350. What is probably happening here is the capacitor connected across the output winding of the transformer may be resonating with the windings producing a peaked response and subsequent high voltage. The solution is to try differing values of capacitance here. It is a trade off between on load voltage...regulation....and current consumption. Some power supplies idle drawing only 250mA giving 350 volts whilst others draw 650mA in the same situation. Don't worry about the current consumption (unless this is a big issue for use in the field) since it will be better to go for the best regulation even if the reduced voltage (say 280v) cuts your power output slightly. Q A newly built Paraset is not working in receive. The regeneration control appears to work in that it increases the hiss in the phones but the receiver still does not receive any signals. The components all check ok, what is wrong? A Turning up the regeneration control will cause the voltage on the anode to fall. It would be wise just to check this happens since it is a good indicator that the basic receiver is trying to work. The fault almost certainly lies with the receiver coil. Assuming the coil in not open circuit the problem is probably one of feedback being applied out of phase. Check that you have correctly identified the cathode tap and the earth connection of this coil. Swap them over if you find them to be incorrect. If the rx still does not work then Note the direction of the cathode winding on the coil former and ensure that the large part of the winding IS wound in the same direction. If the windings are not wound in the same direction the only answer is to rewind the coil correctly.
|
