841
North American Shortwave Pirate / Re: UNID 6932.06 AM 2328 UTC 22 September 2018
« on: September 22, 2018, 2349 UTC »
It might be gonve, or it slid down to 6935 briefly and then off. Not sure. 
Shortwave Pirate Radio In North America And Around The World, And Other Signals That Go Bump In The Night
We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations.
Always consult with the appropriate authorities if you have questions concerning what is permissible in your locale.
Depends upon how they calculate cable loss in the analyzer (and here I am showing my ignorance
) but it sounds like they are just taking the return loss (which is related to VSWR) and calling that the cable loss. Return loss magnitude is higher with a proper load and near zero with a short or an open as the load. It's a shorthanded way to get a result. However, you would have to use either an short or an open at the other end to make this "right".
Take a look in the manual and see if they ask you to put a short or an open at the end of the coax.
Edit: I said to myself, jeez, just go look this up myself.
Page 19 of the MFJ-259C manual
So I was right. Ignore the loss value with a dummy load attached. Use an open end with "Coax Loss mode".
Any filter will have some loss within its passband, while still presenting a "reasonable" (~close to Zo) impedance on either port. The LPF does what you say by introducing loss within the passband inline with the coax. That loss will reduce the impedance variation seen at the far end of the coax. Thus it is "fooling" (there's that word again
) the radio into thinking it is seeing an impedance closer to Zo.
It's an old trick; use it all the time in the lab to calm harsh impedances and isolate.
Nothing magical about it. You don't even have to use a LPF. Anything with loss will do the same thing. In this way it's not different than extending the coax by the distance to generate the same amount of loss.
The longer the coax run is, the more loss there will be and the lower the SWR will appear due to the losses partially "masking" the mismatch reflections, as others have stated.
In any case, seems like you're in good shape.
Does the analyzer give you any estimate of the loss (in dB) of the cable? If not, don't worry about it.
This is along the lines of some of the articles on G5RV antennas that I have read - best resonance somewhere 11-16 MHz, depending upon the situation.
That's some serious disclaimer activity there.
It's a question of management of expectations. If you aren't expecting VOA-levels of coverage then you may find it satisfactory.
I think that The Relay Station runs 1/2 W into a "good" antenna during the daytime occasionally and people actually do hear it.
I prefer dead-bug style - shortest connections between components in some cases.
Yes, completely true.
To the O.P., You may want to connect your antenna analyzer to the antenna at the feedpoint (if possible) and avoid the coax to get a true reading of the antenna. Assuming it doesn't involve gymnastics, I prefer to do that instead of "backing out" (calculating what the antenna really looks like) through software or a Smith Chart and avoid possible human error.
Then, put a dummy load at the end of your coax and connect your analyzer to the other end of the coax. You should see loss but hopefully you will see something like Z = 50+j0. This is a good check to be sure that your coax isn't screwing things up more than it should. Find out what the expected loss (per unit of distance) is for your coax and see if the loss makes sense.
Optimal transfer to/from the radio is when it is presented with ~50+j0 Ohms. The antenna tuner/transmatch does the best it can to approach that, when tuned properly. In other words, it fools the radio into into thinking it is seeing as close to 50+j0 Ohms as possible.
Also, optimal transfer to/from the antenna likely happens at some impedance other than 50+j0. The tuner/transmatch does the same "fooling" bit for that side too. Imagine that.
On a related subject, I don't understand this complete and all-out attempt to avoid the usage of a transmatch/antenna tuner in ham radio. The way I read some articles, I come away with the feeling that some authors feels like it's utter failure to have to use a tuner, which is ridiculous to me. I get not wanting to have to lug one around if you are backpacking or something but otherwise face up to the physics and suck it up, buttercup. You need to match to the load or accept the losses.
Show Posts
This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.
842
North American Shortwave Pirate / UNID 6954.97 AM-> 6955 USB 2344 UTC 22 September 2019
« on: September 22, 2018, 2345 UTC »
Overmodulated rock music. SINPO 22221 into an SDR in Virginia.
2355 - caught bits of what I think is George Thorogood and The Destroyers, "I Drink Alone".
0010 - music stopped mid-song then some sort of computerized announcement and then TX off.
0013 - back on in USB and very strong now.
0014 - George Thorogood and The Destroyers, "I Drink Alone"
0041 - SSTV
2355 - caught bits of what I think is George Thorogood and The Destroyers, "I Drink Alone".
0010 - music stopped mid-song then some sort of computerized announcement and then TX off.
0013 - back on in USB and very strong now.
0014 - George Thorogood and The Destroyers, "I Drink Alone"
0041 - SSTV
843
North American Shortwave Pirate / UNID 6932.06 AM 2328 UTC 22 September 2018
« on: September 22, 2018, 2329 UTC »
Reasonable carrier but weak modulation. I hear music with male vocalist at 2329 UTC.
844
European Pirates and Private Stations / Re: Radio 319 5050>5055 AM 1355 utc 22 sep 2018
« on: September 22, 2018, 2118 UTC »
Seems like the TX went off the air sometime around 2045 UTC.
845
European Pirates and Private Stations / Re: 3905 AM R. Alice 1931 UTC 22 Sep 2018
« on: September 22, 2018, 2046 UTC »
Someone whistling over the LSB at 2041 UTC.
846
Equipment / Re: G5RV Jr. on the Antenna Analyzer
« on: September 22, 2018, 2045 UTC »Ran some coax loss tests with the line terminated at various sections with the dummy load and unterminated.
Unterminated, the entire segment (about 85 feet), connectors and all, produced a loss of about .7db.
With the dummy load hooked up, losses were high (about 12 db for the entire segment). This is where I reveal my ignorance of dummy loads and loss. When connected to shorter segments, the loss was higher.
Depends upon how they calculate cable loss in the analyzer (and here I am showing my ignorance
) but it sounds like they are just taking the return loss (which is related to VSWR) and calling that the cable loss. Return loss magnitude is higher with a proper load and near zero with a short or an open as the load. It's a shorthanded way to get a result. However, you would have to use either an short or an open at the other end to make this "right". Take a look in the manual and see if they ask you to put a short or an open at the end of the coax.
Edit: I said to myself, jeez, just go look this up myself.
Page 19 of the MFJ-259C manual
Quote
6. Defective Cable: Erratic SWR readings will also occur if your coax isn't 50 ohms. Kinks,
water ingress, oxidation, corrosion, bad connectors, improper construction, and even
mislabeling by the manufacturer may be the cause. Check SWR with a dummy load installed
at the far end of the cable. If it is elevated or the Impedance (Z) fluctuates very much as you
tune the analyzer's VFO, suspect defective cable.
7. Lossy Cable: Coax may exhibit excessive loss from contamination or may have too much
normal attenuation for use at higher operating frequencies. To measure loss, unhook the cable
and use the analyzer's Coax Loss mode to check it against the factory specifications.
So I was right. Ignore the loss value with a dummy load attached. Use an open end with "Coax Loss mode".
847
Equipment / Re: G5RV Jr. on the Antenna Analyzer
« on: September 22, 2018, 2020 UTC »If you have a hf low pass filter (ie cuts off above 10m) handy, place it inline and check swrs again on the antenna system. I find it moderates the radical swr readings from band to band
Any filter will have some loss within its passband, while still presenting a "reasonable" (~close to Zo) impedance on either port. The LPF does what you say by introducing loss within the passband inline with the coax. That loss will reduce the impedance variation seen at the far end of the coax. Thus it is "fooling" (there's that word again
) the radio into thinking it is seeing an impedance closer to Zo.It's an old trick; use it all the time in the lab to calm harsh impedances and isolate.
Nothing magical about it. You don't even have to use a LPF. Anything with loss will do the same thing. In this way it's not different than extending the coax by the distance to generate the same amount of loss.
848
Shortwave Broadcast / WRMI 7570 KHz 0325 UTC 22 September 2018
« on: September 22, 2018, 0336 UTC »
In Spanish but crappy computer-generated text-to-speech (with terrible pronunciation) and in a very heavy American accent on top of that. This is really bad. I'm not a Spanish speaker but I can tell that this sounds like shit.
849
North American Shortwave Pirate / Re: YHWH 7465 AM 0228 UTC 21 SEP 2018
« on: September 22, 2018, 0325 UTC »
Good carrier into Western Ontario @0300 UTC 22 Sept 2017 but modulation is very, very low. I'm not even sure that I heard any.
TX off at 0322 UTC.
TX off at 0322 UTC.
850
Equipment / Re: G5RV Jr. on the Antenna Analyzer
« on: September 22, 2018, 0221 UTC »I connected the feed line to a dummy load at the antenna end and connected the analyzer inside the shack. For the most part, I got 1:1, with an occasional 1.1:1. So, for 85 feet of coax I'm pretty happy with that.
The longer the coax run is, the more loss there will be and the lower the SWR will appear due to the losses partially "masking" the mismatch reflections, as others have stated.
In any case, seems like you're in good shape.
Does the analyzer give you any estimate of the loss (in dB) of the cable? If not, don't worry about it.
Then, I connected the analyzer to the G5RV Jr. via a 3 foot patch cable.
The "resonant" frequency appears to be 15.540, with somewhere in the 10 meter band being the next best thing. Can't wait for 10 meters to open up full time!
This is along the lines of some of the articles on G5RV antennas that I have read - best resonance somewhere 11-16 MHz, depending upon the situation.
851
North American Shortwave Pirate / Re: Mix Radio International 6870 USB 2221 UTC 21 Sep 2018
« on: September 22, 2018, 0148 UTC »
Listening in Ontario. Very nice signal for the past hour or so. SINPO 55445. There is a dead carrier on ~6870.89 but it is much weaker and not causing too much QRM.
It's rare that SSB sounds this good. I see approximately 13 - 14 KHz bandwidth.
I also see some unintended sideband though - between DC and ~700 Hz there is almost no rejection of the unintended and the LSB is as strong as the USB, with much higher attenuation above ~700 Hz. It is sort of listenable on the LSB but the audio quality suffers for the reasons above.
Cheers.
EDIT: propagation went into the toilet around 0204 UTC. Faded down to noise level.
It's rare that SSB sounds this good. I see approximately 13 - 14 KHz bandwidth.
I also see some unintended sideband though - between DC and ~700 Hz there is almost no rejection of the unintended and the LSB is as strong as the USB, with much higher attenuation above ~700 Hz. It is sort of listenable on the LSB but the audio quality suffers for the reasons above.
Cheers.
EDIT: propagation went into the toilet around 0204 UTC. Faded down to noise level.
852
Equipment / Re: Mod Black Cat Beacon Kit
« on: September 22, 2018, 0009 UTC »Quote
Note: This is not an official authorized mod. Black Cat Systems had nothing to do with this mod.
Build and test your original kit first the way it was originally designed.
Then if you choose to do this mod, do it while knowing that it started out working OK.
If you mess up your kit, don't blame Black Cat Systems.
When you do this kind of crazy mod, it is totally your own responsibility.
Hams can use this mod for a ham band beacon
With the warnings having been duly admonished, onward to the actual beacon mod:
That's some serious disclaimer activity there.
853
The RF Workbench / Re: New here, and my journey building a SW xmtr
« on: September 21, 2018, 2355 UTC »I bet half a watt with a nice inverted v at the highest height you can reasonably get would perform as well as a ten watt run into a vertical or shitty nonoptimized dipole.
It's a question of management of expectations. If you aren't expecting VOA-levels of coverage then you may find it satisfactory.
I think that The Relay Station runs 1/2 W into a "good" antenna during the daytime occasionally and people actually do hear it.
If you can do breadboard shit go for it but I take the easy way out and would try copper board manhattan style coz that's the way I think and might work better.
I prefer dead-bug style - shortest connections between components in some cases.
854
Equipment / Re: G5RV Jr. on the Antenna Analyzer
« on: September 21, 2018, 0421 UTC »Transmission lines with high losses will give false readings of low VSWR due to the losses attenuating the signal before it gets back to the meter.
... The more losses you have in the cable, the better your SWR will 'appear' to be with a meter located at the source.
Yes, completely true.
To the O.P., You may want to connect your antenna analyzer to the antenna at the feedpoint (if possible) and avoid the coax to get a true reading of the antenna. Assuming it doesn't involve gymnastics, I prefer to do that instead of "backing out" (calculating what the antenna really looks like) through software or a Smith Chart and avoid possible human error.
Then, put a dummy load at the end of your coax and connect your analyzer to the other end of the coax. You should see loss but hopefully you will see something like Z = 50+j0. This is a good check to be sure that your coax isn't screwing things up more than it should. Find out what the expected loss (per unit of distance) is for your coax and see if the loss makes sense.
855
Equipment / Re: G5RV Jr. on the Antenna Analyzer
« on: September 20, 2018, 2202 UTC »Someone I know, who should know better as a trained electronics and radio tech, said a tuner simply fools the radio into thinking it sees 50 ohms.
This is not the case.
A tuner, or transmatch, is often a two port device that transforms the z seen by at least one of the ports. Also, the power that would be reflected by a high swr as seen by the transmitter end is re reflected back to the load until it leaves the load because the transmatch becomes the proper termination seen by each port - the low z side sees low z, the high z sees high z and the transmatch handles the transfer of energy between the two. And it's a two way affair, optimising power transfer between the ports regardless of source.
Optimal transfer to/from the radio is when it is presented with ~50+j0 Ohms. The antenna tuner/transmatch does the best it can to approach that, when tuned properly. In other words, it fools the radio into into thinking it is seeing as close to 50+j0 Ohms as possible.
Also, optimal transfer to/from the antenna likely happens at some impedance other than 50+j0. The tuner/transmatch does the same "fooling" bit for that side too. Imagine that.
On a related subject, I don't understand this complete and all-out attempt to avoid the usage of a transmatch/antenna tuner in ham radio. The way I read some articles, I come away with the feeling that some authors feels like it's utter failure to have to use a tuner, which is ridiculous to me. I get not wanting to have to lug one around if you are backpacking or something but otherwise face up to the physics and suck it up, buttercup. You need to match to the load or accept the losses.