181
Longwave Loggings / Re: New to longwave
« on: February 28, 2020, 1256 UTC »
Thanks. I will try contacting him again.
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I have one of those. It works, but the one I have from www.rescueelectronics.com works a little better.
I would recommend caution with the bypass switch that the universal-radio filter has. The capacitance across the switch can degrade the overall rejection of the filter by allowing a little bit of signal to bypass the filter itself.
Also be sure to use a good quality jumper cable between the filter and the radio. Last year I noticed detectable signals in the stop band of a LF LPF I was using. It turned out that the jumper I was using was the problem. I replaced it with a different jumper and all was well again. Checking the jumper out on a Spectrum Analyzer I found that the poor jumper degraded the filter stop band by more than 20 dB. When I cut the jumper open I found very poor braid coverage.
Be careful about the 20W in the AMBC. Depending on where they put the LPF cut off frequency, that 20 watts you are reading may be a combination of the fundamental and harmonics.
I used my KX3 to check into a 5 MHz Navy MARS net once (since it was Navy MARS you know that was a few years ago). I did not modify anything for MARS ops, but it is possible that I was only able to do so because the radio was capable of 60 Meter band operation. I never tried it on other MARS frequencies.
It’s my understanding that Icom still builds their radios in Japan. They might source parts from China, but they kept production in Japan.
Or it is a way of saying that the SDR market is highly competitive and you have to bring out improved products to stay ahead of your competitors.
Can you provide a reference regarding these “issues”? EHam gives it a score of 4.8 from 30 reviews. SDRPlay is a solid company with popular products and lots of tutorials.
I don’t think the RSP2 has any more “issues” than any other SDR in this price range. All of these SDRs have common issues regarding front end filters and needing to be careful not to transmit near them, even the expensive ones.
IZS4, I think you will be happy with your RSP2...there is a lot to learn about SW settings, but you are going to have fun doing so.
All practical antennas have nulls and lobes. The DX is always in a null on the antenna you are using. Having choices means another one might have the DX in a lobe.
You can never have enough antennas.
I often marvel over discussions of signal loss. Some people will agonize over a tenth of a dB loss in connectors and others go “yeah....6 dB....that’s only an S-unit...I can live with that...”
And they are both right. It is all situational.
If your link has plenty of margin, a little extra loss is no big deal. If you are on the hairy edge, it can be a deal breaker. If all you listen to is your local NWS station, almost any antenna will work. If you are trying to hear one 300 miles away, you need a better antenna and feedline.
If you perform a link calculation for a free space path, a 3 dB increase in signal will increase your range 1.41 times. In practice (where a lot of other factors are also in play) you probably won’t see that, but you might see something on the order of a 20% increase in range. Would you notice a 20% range improvement on a daily basis? Maybe not, particularly on analog modulations where you are subjectively trying to decide whether signals are better or not.
For digital signals, 3 dB can make or break you depending on how much link margin you have. The BER curves for common error correcting code modulations are steep. If you are on the wrong side of the curve you get nothing, an extra dB might push you far enough to the other side of the curve to give you near perfect copy. This effect is well documented in the LMR industry where digital modulation (P25, DMR, etc) has firmly taken hold. Weak signal intelligibility is either good or non-existant.
The big reason to worry about every dB is because losses are accumulative. You might spend extra money for better transmission line and then throw the additional gain away by using poor connectors.
If you are designing for situations where you expect to work with marginal signals as a matter of course (e.g. radio astronomy, EME, etc) you are going to chase every dB. If you are putting up an antenna system for casual listening, you can be more willing to make compromises.
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182
Longwave Loggings / Re: New to longwave
« on: February 27, 2020, 1133 UTC »
Please let me know if you get a response from Rescue Electronics. They didn’t answer an email I sent them a few months back (as I noted earlier). You should be safe with a Paypal purchase as you can get your money back if he doesn’t respond. The filter does work well.
The owner is W1VLF, who has several useful Youtube videos available.
The owner is W1VLF, who has several useful Youtube videos available.
183
Equipment / Re: NEMP Rated surge arrestor
« on: February 24, 2020, 0301 UTC »
The isolation capacitor in series with the center conductor is large enough for VHF and higher, but not for HF.
184
Equipment / Re: Spitfire Am transmitter
« on: February 23, 2020, 1314 UTC »
Outdoor unit:
http://talkinghouse.com/range-extender-2.5.htm
https://www.hobbybroadcaster.net/reviews/iss-range-extender-2.5-talking-house-iam-radio.php
The antenna tuner in the outside unit looks a lot like that used in the inside unit (https://images.app.goo.gl/BMwyMH8ZS4LTTBT99).
I don’t know if they actually put the final amplifier outside or not.
Note the patent links on this page. They provide an explanation of how it works.
http://www.prc68.com/I/TalkingHouseTransmitter.html
http://talkinghouse.com/range-extender-2.5.htm
https://www.hobbybroadcaster.net/reviews/iss-range-extender-2.5-talking-house-iam-radio.php
The antenna tuner in the outside unit looks a lot like that used in the inside unit (https://images.app.goo.gl/BMwyMH8ZS4LTTBT99).
I don’t know if they actually put the final amplifier outside or not.
Note the patent links on this page. They provide an explanation of how it works.
http://www.prc68.com/I/TalkingHouseTransmitter.html
185
Equipment / Re: Spitfire Am transmitter
« on: February 23, 2020, 1300 UTC »
As I remember, the amplifier and matching network are out at the antenna. The coax merely brings a low level RF signal from the indoor unit to the outside amplifier. So rather than put everything in one box, they split it into two.
186
Equipment / Re: NEMP Rated surge arrestor
« on: February 23, 2020, 1246 UTC »
The frequency limits they show are real too. I saw an installation where the installers used similar surge supressors for the HF antennas. The antennas were dead as a door nail. Replacing the supressors with ones rated for HF made everything good again.
187
Longwave Loggings / Re: New to longwave
« on: February 23, 2020, 1235 UTC »Would it be this filter? Or is this an old model?
https://www.universal-radio.com/catalog/filters/1143.html
A lot cheaper.
I have one of those. It works, but the one I have from www.rescueelectronics.com works a little better.
I would recommend caution with the bypass switch that the universal-radio filter has. The capacitance across the switch can degrade the overall rejection of the filter by allowing a little bit of signal to bypass the filter itself.
Also be sure to use a good quality jumper cable between the filter and the radio. Last year I noticed detectable signals in the stop band of a LF LPF I was using. It turned out that the jumper I was using was the problem. I replaced it with a different jumper and all was well again. Checking the jumper out on a Spectrum Analyzer I found that the poor jumper degraded the filter stop band by more than 20 dB. When I cut the jumper open I found very poor braid coverage.
188
Longwave Loggings / Re: eLoran 100 kHz 1252 UTC 20 Feb 2020
« on: February 20, 2020, 1426 UTC »
Good signal in Midland 1423Z. Note that the KiwiSDR has a decoder built in as an extension. GRI is 8970.
189
Equipment / Re: Any Elecraft KX3 owners?
« on: February 18, 2020, 1035 UTC »A lot of kx3 owners I know of are selling their kx and getting these things;
https://www.youtube.com/watch?v=gwHbZasHleQ
Simple one diode-ectomy to enable wideband tx, and they nicely placed a rather obvious arrow pointing at the diode to dissect. 20w even on ambc plus a transmatch that will match shorts to opens. Draws about 500 mils on rx with screen off.
Be careful about the 20W in the AMBC. Depending on where they put the LPF cut off frequency, that 20 watts you are reading may be a combination of the fundamental and harmonics.
I used my KX3 to check into a 5 MHz Navy MARS net once (since it was Navy MARS you know that was a few years ago). I did not modify anything for MARS ops, but it is possible that I was only able to do so because the radio was capable of 60 Meter band operation. I never tried it on other MARS frequencies.
190
General Radio Discussion / Re: Another Pride of China portable radio
« on: February 17, 2020, 1323 UTC »
It's all Made in China now, including Kenwood Icom Yaesu and the smart device or computer you used to type this comment.
It’s my understanding that Icom still builds their radios in Japan. They might source parts from China, but they kept production in Japan.
191
SDR - Software Defined Radio / Re: SDR reception
« on: February 15, 2020, 1344 UTC »QuoteThe RSPdx is a replacement for the highly successful RSP2 and RSP2pro SDR receivers, which have been extensively redesigned to provide enhanced performance with additional and improved pre-selection filters, improved intermodulation performance, the addition of a user selectable DAB notch filter and more software selectable attenuation steps.
This is a fancy way of them saying the RSP2 has issues and thus it needed a re-design. Buy the RSPdx instead.
Or it is a way of saying that the SDR market is highly competitive and you have to bring out improved products to stay ahead of your competitors.
Can you provide a reference regarding these “issues”? EHam gives it a score of 4.8 from 30 reviews. SDRPlay is a solid company with popular products and lots of tutorials.
I don’t think the RSP2 has any more “issues” than any other SDR in this price range. All of these SDRs have common issues regarding front end filters and needing to be careful not to transmit near them, even the expensive ones.
IZS4, I think you will be happy with your RSP2...there is a lot to learn about SW settings, but you are going to have fun doing so.
193
SDR - Software Defined Radio / Re: SDR reception
« on: February 14, 2020, 1330 UTC »
First thing I would check are the gain settings. If they are too high, you will get odd behavior. There is some guidance in this video. If you are trying to listen to yourself on 2M, overload seems like a definite possibility.
https://youtu.be/bGHwY8JWaGE
I have also noticed 10 MHz WWV reception is not as good as I remember and this is on multiple receivers. It also seems like there might be some local interference. It could also be propagation conditions too.
https://youtu.be/bGHwY8JWaGE
I have also noticed 10 MHz WWV reception is not as good as I remember and this is on multiple receivers. It also seems like there might be some local interference. It could also be propagation conditions too.
194
SDR - Software Defined Radio / Re: SDR recommendation......
« on: February 13, 2020, 1245 UTC »I'm a big fan of passive antennas over active. For general purpose receive, a sky loop is hard to beat.
If it's so good then why do you have 17 antennas?
I have two HF antennas. One is for Rx and the other is for Tx. My Rx loop is about 60m but hey no one is perfect.
All practical antennas have nulls and lobes. The DX is always in a null on the antenna you are using. Having choices means another one might have the DX in a lobe.
You can never have enough antennas.
195
Equipment / Re: VHF/UHF coax recommendation
« on: February 13, 2020, 1236 UTC »Yep, that .6 dB/100ft. is killer. 1/10 of an S unit. Gonna make a big difference on the repeaterWAY easier to string up.
This is why I went with RG6 vs LMR-400 for my discone. A few dB extra loss over the length of the run. I have a 4:1 splitter that I can connect here in the shack to feed 4 radios, with a 6 or 7 dB reduction in signal of course to each radio vs directly connecting the antenna to one radio. I can just barely hear the difference even on very weak signals.
I often marvel over discussions of signal loss. Some people will agonize over a tenth of a dB loss in connectors and others go “yeah....6 dB....that’s only an S-unit...I can live with that...”
And they are both right. It is all situational.
If your link has plenty of margin, a little extra loss is no big deal. If you are on the hairy edge, it can be a deal breaker. If all you listen to is your local NWS station, almost any antenna will work. If you are trying to hear one 300 miles away, you need a better antenna and feedline.
If you perform a link calculation for a free space path, a 3 dB increase in signal will increase your range 1.41 times. In practice (where a lot of other factors are also in play) you probably won’t see that, but you might see something on the order of a 20% increase in range. Would you notice a 20% range improvement on a daily basis? Maybe not, particularly on analog modulations where you are subjectively trying to decide whether signals are better or not.
For digital signals, 3 dB can make or break you depending on how much link margin you have. The BER curves for common error correcting code modulations are steep. If you are on the wrong side of the curve you get nothing, an extra dB might push you far enough to the other side of the curve to give you near perfect copy. This effect is well documented in the LMR industry where digital modulation (P25, DMR, etc) has firmly taken hold. Weak signal intelligibility is either good or non-existant.
The big reason to worry about every dB is because losses are accumulative. You might spend extra money for better transmission line and then throw the additional gain away by using poor connectors.
If you are designing for situations where you expect to work with marginal signals as a matter of course (e.g. radio astronomy, EME, etc) you are going to chase every dB. If you are putting up an antenna system for casual listening, you can be more willing to make compromises.