Hmmm, on 2nd thoughts, my Kenwood tranceiver has a 25khz 'marker' switchable on/off. This was to help with any non linearity in the tuning indicator...drift etc. That is what the pull on marker is for(probably).
BFO must be skullking in the shadows to the left somewhere.
Cheers,
Doug
2. I had all Kenwood gear - very good brand.
that RX will do everything you need to do with no problems.
3. Pic DSC01277 shows that you have tuned to 20.9Mhz and not 21.9MHz go 1 Mhz up.
4. The S meter is very useful. Each step should represent 6db. But the steps are not calibrated real well in commercial receivers(difficult to do properly and expensive too!!) and will probably be 4db per step. What this means is that the Jupiter signal (12db over the noise floor) should make the S meter read S2 to S4 - pretty good signal.
5. Antenna looks good - like your documentation ... keep it up.
6. For a bit of practice try listening on from 21.0 to 21.25MHz using USB - see what you can hear. This band runs hot and cold If you hear nothing the band is probably dead for earth signals good! (never thought I'd hear myself saying that) it means the Jupiter signal will be better to receive.
7. Re: The Controls - Not much to say - Doug said it all. The only thing to say is that one site said to construct an "Envelope Detector" you do NOT need to - the AM demodulator (AM mode) IS an envelope detector.
Comment about USB (Upper sSide Band). USB is a very simple mode think about it like this: When you speak into the mic. your voice frequencies are moved to the carrier frequency that you selected. The voice freqs go from (say) 300Hz to 4000Hz now if you set the transmitter to 20,000,000Hz (20MHz.) when you talk the transmitter moves your voice freqs to the band 20,000,0300Hz. to 20,004,000Hz. When you stop talking nothing is transmitted. When you receive on that frequency the receiver moves the freqs round the carrier freq to the audio band and that's it. In USB you get in the audio band what was in the RF band.
Do you still want to know why the dipole is connected in the centre? Vertical of 0.25 wave is also a dipole fed at one end - answer is interesting involved and boring!!
Pretty unlikely, Doug. The receiver already has SSB capability. This, by the way, Barry, could be an automatic set up. Accepted convention is that Lower Side Band (LSB) is used for frequencies below 15MHz (I think) and Upper Side Band (USB) for above that. This of course is merely a man-made contrivance to avoid confusion. It won't worry you in your project.
I managed to get some more information from your image - which was not apparent on the original viewing: the lower drum is indeed a band spread control (although you'd be aware of that anyway, I guess).
Well John I suppose it depends on how old that receiver is. My Kenwood TS520 has switch selectable upper, lower or CW.(But of cource it needs it for TX) The Amature conventions were not necessarily used comercially last time I had the urge to go SWLing, and come to think of it I might have monitored a few Amature comunications that were using the opposite sideband occasionally to beat interference.
What about the FRG7? never seen one myself, does it not have a BFO? How does one resolve 2+ ssb duplex transmissions that have a slight offset to each other? VFO offset?.............more gobledygook
But then again I recalled what the marker was in my follow up post.
In anyevent I think Jupiter would best be monitored on AM. One would need the wider bandpass I should think.
Doug the FRG7 was a basic communications receiver that does indeed have a bfo, but rather broad and unswitched IF selectivity so it was just as wide on AM or SSB.
Valve? Eddystone? Next you'll be using words like "Wharfedale", "Quad" and "Practical Wireless" ... Sorry.
Jerry.
Tee hee. Settle down, Jerry.
Geoff, I'm sorry, I must be getting my model numbers mixed up. I thought the FRG7 was a transceiver (low output device, set back dials and such with a blue background). *edit* I just did a quick bit of research. I was confusing it with the FT-7.*/edit*
Doug, it is a convention - not a requirement - and one which is (or was) generally adhered to by commercial broadcasters. Then again, so are the various band plans - but you don't need to listen for very long to see that this is flouted.
Barry, ignore this chit chat. It won't worry you. As Doug said, I'd start using the AM mode of listening and, just for interest's sake, experiment with the other modes.
I downloaded a trial version of "Radio-Jupiter Pro" from the radiosky site and ran the code to see when the signals would be up. The various modes are up for only an hour to an hour and a half - real hit and miss if you listen at random times!!
According to their prediction:
27-Oct-2006 C mode is from 08:41z to 10:08z
28-Oct-2006 B mode is from 08:42z to 10:28z
29-Oct-2006 A mode is from 08:43z to 09:51z
and ---------C mode is from 09:49z to 10:25z
30-Oct-2006 B mode is from 10:05z to 10:22z
31-Oct-2006 A mode is from 08:58z to 10:20z
-------------IoA mode is from 08:58z to 10:20z
--------------B mode is from 08:45z to 09:00z
It looks as if you have to really be prepared for it.
Rgds,
Jerry.
PS.
John,
I thought you'd like the bit about the extra words.
Hmmm....All very interesting stuff. I am paying close attention to your, "chit chat". I had no idea that my little radio astronomy thread would produce so much conversation and interest. I am still a little stunned by the overload of information you champions have provided.
I put up another dipole today, this one just for cb comms. I used the wire out of a mig welder which is plenty strong enough for the job.
I tried making up a little coil that I have seen on other antennas that is supposed to stop something happening. Something to do with RF? Anyway, its three loops approximately 9cm in diameter. It was just a guess. This is for 27mHz and the dipole lengths are about 2.7 metres. Lets see how we go.
I think my power supply may need a change as it is out of an old computer and only supplies about 10 volts. I beleibe i need about 12 volts.
Heres a pic of the new dipole (above the observatory this time.)
And a little pic of my other project for this weekend. Cant wait to paint it....groaaaaannnn!
You are certainly a busy boy, Barry. Incidentally, where are you? You might have said at some stage but, if so, I've forgotten.
The little coil is probably a simple RF choke which is designed to suppress unwanted radio frequency signals on the feedline. Your new dipole for 27MHz should work well; the only problem you might come across is that your dipole is horizontally polarised whereas most CB transmissions tend to be vertically polarised (in that most users employ vertical aerials). In theory cross polarisation will result in something around a 20 dB reduction in received signal strength - in practice this is somewhat less but is still noticeable. Nevertheless it probably won't worry you, particularly if you are using it for local communications.
Incidentally, if you are in fact interested in radio in its various facets, have you thought of joining the ranks of amateur radio licencees? I only ask as there is new licence category - and which is not difficult to achieve - known as the Foundation Licence. While the privileges of this licence are restricted to some extent it will give you the opportunity to talk to many fellow amateurs who are well versed in the subject.
Just a thought.
P.S. Yes, like others on this site I'm a 'Ham'. (VK2BZB).
I have had the thought on polarisation. I have a HAM radio friend only 2 suburbs away with a vertically polarised antenna and it is ok picking him up, but I think polarisation combined with the fact that my power supply only puts out 10 volts, is a bit of a problem.
I am considering applying for the licence and sitting the test. Time and money will play their usual part. THe pace is slow but continues steadily mate.
I am also looking at alternative antennas that dont look like a sack of s**t above my observatory, as it is in the front yard for all neighbors and passers by to see. I looked at a quad, but for 18 to 30 mHz, the size is prohibitive.
I may have to consider higher frequencies and changing to satelite tracking stuf and uhf, although as far as I can tell, most natural space phenomena are at frequencies hf and below and thats where my interest really lies.
Hi Jerry, at the risk of spaming Baz's thread, which I'm really not, You mentioned a 'delta' match for TV yagis(when I was discounting the value of baluns). I don't know book fulls about TV antennae, are you suggesting that they are log periodic in their basic operation?
Hmmm, since I have bumped this thread back into activity of sorts, I see Polarization has reared its ugly head.
Who wants to listen to the 'big 10/4' set anyway?
Is it known what Jupiter's polarization is? could be circular rather than either V or H.
Barry There is a heck of a lot of action on the neutral Hydrogen band around 21cm. A good Higain array, (circularly polarised I might add) for 21cm would just about fit in your pocket. The neighbours would need to borrow your scope just to see it! Better still a parabolic array would not be impossible to realize.
Cheers,
Doug
OOOOHHHH! Now that does sound interesting... Thank you! I think I will have to have a look into that one. I may need to update the receiver though....21 cm, thats vhf or uhf isnt it?
Doug, my understanding of polarisation so far is a purely physical thing. As I understand, a vertical whip to a horizontal diplole, does not communicate as well as vertical to vertical, or horizontal to horizontal. I don't see how Jupiter could be polarised except that the planet and its electromagnetic field is circular or spherical of sorts, acting as a virtual antenna, rather than a peice of wire........ unless we are talking about the longitudinal lines of its magnetic fields as straight linear, in which case these would change through the hours, days, months and years as its position, axis and rotation changes in relation to our position, axis and rotation.
I'm not an authority on this, just applying simple logic to the limited knowledge I have on the electromagnetic spectrum and astronomy in general.
I've had a crack at it, now tell me....did I get it right? Was I close? LOL
I did a search on jupiters polarisation and came up with many results. Looks like either circular or eliptical. Heres a shameless cut and paste from one site....
Observations of Jupiter made at the Owens Valley Radio Observatory with wavelengths of 10 and 21 cm indicate that the radiation has a small and variable circularly-polarized component which has a more distinct double structure than the rest of the radiation. The maximum degree of circular polarization is about 4%, and the variation is correlated with Jupiter's rotation. From the measurements it is shown that the polarity of Jupiter's magnetic field is opposite that of the earth's and that the field strength at 2.5 radii from the center of the planet in the equatorial plane is 1.7 gauss with a very large uncertainty. (Author)
and thats where my interest really lies.
