VK Logger Ham Radio Forum Archive

I received a V2 Agile PLL from Graham today. PLL001.jpg It is not committed to a particular application, but rather an experimental device with some initial projects lined up. For that reason, I will use a different controller and provide facility to update firmware and configuration from outside th...

...Hope that makes ensue? Sense? Ok and good, but your solution might have dealt with only some of the sources of PTT. For example, if you the the TRANSMIT button on the front panel, will it cause problems. I am not saying what you have done is poor, it is probably a quite good idea... but the desi...

I repaired a Wouxun KG-UV920P for a friend about 6+months ago. The symptoms were that it drew 10A on tx, both bands, no RF output. The PA FET got very hot, but it was not faulty, the fault was the driver FET. The circuit of the radio is a proprietary secret, and you have to think carefully about buy...

Now I have another problem. I can't find my old balanced tuner. That might be a blessing. A 4:1 balun and coax is looking good. An effective 4:1 current balun on the outside of the wall, and very short length of RG213 or better to the ATU sounds like a good solution for a full wave loop on fundamen...

An exercise on coax and currents... The following diagram (by DK7ZB) contains an error. ... As you know, I1=I2, but there is an error in the markup of currents on this diagram, can you spot it? AS mentioned, coax imposes the constraint that I1=I2. There is an implicity assumption that all currents ...

... Hi Owen, yes I had come to that conclusion. Perhaps a simpler solution would be to manually start the sequence to bypass the LNA then power up the PA and then use the transceiver PTT to operate the Tx relay. Will need to give this scenario some more thought tho'. The mic with a working PTT is a...

... The problem I'm trying to get my head around is how to effectively sequence everything (Rx to Tx) by using the rig's PTT to activate the EME166 sequencer. The 2000X has a max delay before enabling RF of 25mSec...I can't see this as being enough for all the other switching to have taken place be...

An exercise on coax and currents...

The following diagram (by DK7ZB) contains an error.
As you know, I1=I2, but there is an error in the markup of currents on this diagram, can you spot it?

Owen

I checked some measurements I made recently of a pair of RG6 quad shield cables strapped together, and the differential velocity factor of the pair (ie NOT the inside of the coax) was 0.69. I have seen hams talk about numbers nearer 1, but the bottom line is that you have to measure it, and carefull...

Hi Owen, It is digitally generated in an RF chip. Not ideal but it does the job. Regards Andy Andy, Well, that is at question and with no more hints from you about the chip, parameters you have set etc I cannot offer any more suggestion than the common explanation of why most digis that were in ran...

pawsey stub doesn't seem to be suitable either. couldn't get it to tune up so i suspect it has similar limitations to the ferrite idea. also, it's far too fiddly to construct. i'm sure there are 1000 ways to attempt to skin a cat but I was mainly interested in learning about ferrite cored baluns an...

A solenoid choke on the inside or outside of the radome is probably preferable but I'll try a pawsey balun just for the experiment.. it is quite a compact idea. I guess my ideas of using something slipped over the coax as a choke are a no-go :P Another implementation is a coaxial tube over the cabl...

After the discussion in another thread on some aspects of coax operation, here is a device to try your analytical skills out. This is a variation on the shielded ground conductor theme. Wireman say: Coaxial ground kit (#856) With this kit and a scrap piece of any kind of RG8 size coax, you can make ...

Hi Joe, Geoff, I would think that with that antenna, you expect at the bottom of the nominal radiator you will want to accumulate high charge at points in the RF cycle, and to permit that, you must prevent the charge flowing downwards onto the feed line with some kind of choking device. There are a ...

Interesting, because there aren't any APRS weather stations on the VHF network in Tamworth :) ... Didn't notice any weather stations from Tamworth this morning, but I see RF packets relayed from VK2XSO in the Tamworth area (380km north of me). The nearest stations to me are all digis, it is typical...

The coax shield forms a Faraday Screen. The terms Faraday Cage, Faraday Shield, and Faraday Screen are widely used interchangeably to refer to any conducting structure that in some way modifies electric field... and this structure does that... but I think that usage is wrong. If you visit Faraday's...

The original choke is best described as an air cored solenoid of coax, and it it designed to be self resonant at a specific frequency. Whilst the resonator so formed is not a very high Q resonator, it is much higher Q than a resonator formed with a ferrite cored inductor... especially is the materia...

Here is an instrument application of the concept. sampler.jpg If you look carefully, the shield on the coax in the middle is not connected to anything at the left hand end, and grounded ar the right hand end. If current I flows on the inner conductor, then there is an equal current flowing on the ou...

Andy, how do you create the AFSK signal?

Owen

... Will anyone volunteer the answer to "where does it go". The current I1 flowing leftwards on the inner surface of the shield flows around the end of the shield (on the surface) to the outside surface and so there is current I1 flowing to the right on the outer surface of the shield. No...