Messages

211

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.

212

SDR - Software Defined Radio / Re: SDR reception

« on: February 15, 2020, 1344 UTC »

The 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.

213

SDR - Software Defined Radio / Re: SDR reception

« on: February 14, 2020, 1339 UTC »

Look at this video also.  Same thing.

https://youtu.be/L_DdPI1gdfk

214

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.
 

215

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.

216

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 repeater     WAY 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.

217

Equipment / Re: Discone antenna mounting

« on: February 10, 2020, 1904 UTC »

It looks like a an SO239, but the center portion does not have the standard white insulating material. It's just insulated by open air space.

While an N connector will not have the insulating material around the center conductor, most SO239 connectors do...but there is a variant SO-239 that has minimal material, just enough to keep the center conductor socket centered.  Most of the dielectric material between the inner and outer conductor is air.

As near as I can tell, this is done to try to make the impedance of the UHF connector closer to 50 ohms.  UHF connectors are known to be non-constant impedance connectors (unlike BNC or Type N connectors).  The ratio of outer conductor and inner conductor diameters changes across the length of the connector, meaning the characteristic impedance of the connector changes.  This is not a big deal on HF, but becomes more of a concern at VHF and above.

I have never seen these connectors for sale anywhere, but have seen them on SWR/power meters, and on VHF and above radios/antennas.

It sounds like your antenna has this variant of a SO239.  This would make sense to use with a discone.

Redhat is right - this thread would be a lot shorter  if we had included pictures.

218

Equipment / Re: Discone antenna mounting

« on: February 10, 2020, 0941 UTC »

You can't screw a PL259 into an N type socket.

You can force a PL259 into a female N connector...and you will permanently destroy the female N connector when you do.  The center conductor pin will be deformed or broken in such a way that you can’t repair it.  Check your antenna for damage.

Something is wrong when you start talking about having to “thicken up the center conductor with solder”.  It sounds to me like the antenna is damaged.
 

219

General Radio Discussion / Re: Another Pride of China portable radio

« on: February 09, 2020, 1252 UTC »

Chinese radios are often like Harbor Freight tools.  They may be cheap and poorly made - but there are tasks they are perfectly suited for.

220

SDR - Software Defined Radio / Re: First SDR receiver

« on: February 09, 2020, 1237 UTC »

The waterfall is a game changer.

A long time ago I had a Heathkit HO-13 spectrum display connected to my SB-303. This only showed the real time spectrum maybe +/- 50 kHz of what you were tuned to.  It was interesting, but not terribly useful and I soon traded it for something else.

Fast forward a few decades to the era of DSP radios with not only real time spectrum display, but the waterfall that allows you to see things that happened seconds or minutes ago.  Now you are seeing signals that you would have missed in the past - either because you weren’t tuned to that frequency or they were too short in duration.  You are also realizing that something you had dismissed as RFI was in fact a wide band data signal - because you can now see the entire spectrum of the signal.

DXing without a waterfall is like driving while wearing horse “blinders”.  You won’t go back.

There is only so much you can do as far as being to recognize modulation types off of the waterfall.  CW, RTTY, AM, or SSB are pretty easy, but the digital modes are another matter.  This makes sense when you realize that fundamentally many digital modulation schemes are similar.  For instance COFDM is used in many waveforms - but the number of sub carriers and the spacing might be different.  On your waterfall they will look similar.  There are programs available in the commercial market that will perform signal modulation identification but the pricing is way beyond what most of us can afford.

I saw a posting recently by Josh where someone had written something to try to do this.  I have no idea whether it works or not.

https://www.rtl-sdr.com/shazam-style-automatic-signal-identification-via-the-sigidwiki-database/

221

SDR - Software Defined Radio / Re: First SDR receiver

« on: February 08, 2020, 1053 UTC »

The RSP2 is a good SDR.

One thing to keep in mind about it (and most any SDR) is that if a strong signal is present at the input, you may see weird artifacts at other frequencies.  If you have a strong local AM, FM, TV, LMR, etc station nearby, you may need an additional filter.  The RSP2 has filtering built in, but some locations require a little more.  Fortunately, inexpensive filters are available.  Try it out and see if it this is needed.

Along the same lines, SDRuno has a lot of adjustments to tweak.  If performance doesn’t seem very good, it is more likely that some SW parameter needs adjusting rather than the RSP2 being broken.

222

Equipment / Re: Copper Clad Steel

« on: February 07, 2020, 1224 UTC »

An update from Owen, this time looking at ladder line.  Maybe not as bad as previously thought, but still something to be aware of.

https://owenduffy.net/blog/?p=16920

223

Propagation / Re: Grey line map (real time)

« on: February 05, 2020, 1156 UTC »

This is something to be aware of as some propagation prediction programs are using old SSN lookup tables.  This was recently mentioned here:

https://swling.com/blog/2020/01/ham-cap-and-voa-prop-fixing-ssn-look-up-files/

224

Propagation / Re: Grey line map (real time)

« on: February 04, 2020, 1100 UTC »

I use one of the online ones. A solar propagation site has one that works.

http://www.spacew.com/www/realtime.php

While the grayline may be correct, don’t be fooled by the rest of the data at the map link above.  It has been a long time since we have seen a SSN of 86.

"SSN"? I don't even see a reference to an SSN (whatever that is) on the page anywhere. It has the grey line, radio auroral zones, and MUFs delineated and mentioned, and that's about it.

If you look at the graphic, there is a black bar at the bottom where they show the Smoothed Sunspot Number (SSN), which is used to calculate the MUF.

The true current value is on the order of “5” or so.  You can tell that they are using the wrong number because the MUF values the graphic has are unreasonably high.  A SSN value of 86 would have been reasonable 5 years ago - not today.

You can find better numbers for SSN here:

https://www.sws.bom.gov.au/Solar/1/6

225

Amateur Radio / Re: HT Antenna

« on: January 30, 2020, 1339 UTC »

KX4O works as an antenna engineer.  You may find his comments helpful.

https://www.hamradio.me/antennas/ht-antenna-comparisons.html