Out of Band Antenna Tuning

Mystery Ham

Bill -VA3WTB

Is that normally found on Ham gear? I have not had a newer radio in some time, just wondering if they offer that now on most radios.

Chris DL5NAM

Mister Mystery - how you will tune out of band? How should it work without RF at a SDR? TX out of band ?
Don't know from what country you are.  A real Ham don't do it :-)

73 Chris DL5NAM

Mystery Ham

Many newer radios have "general receive" capability that allows for monitoring the multitude of shortwave broadcast bands.

Bill -VA3WTB

Yes I know about general coverage, what I am asking is,,,do most radios have  inductance, capacitance adjustments for receive?

Mystery Ham

HCampbell WB4IVF

That’s an interesting suggestion, but I don’t think it would help much, if any, in the HF SWL bands if you have a decent antenna, due to the ambient noise.  While my LDG autotuners have the manual C and L controls but I don’t bother using them, or my manual tuners, for listening for that reason. 

Adjusting L and C manually might help if you use a really, really inefficient antenna (like a mobile whip for the low HF bands), but other than that case I don’t see the benefit.  Even in that case I think you’d be better off getting/building a good Rx antenna.  I use beverages but there are many other types that don’t require nearly that much real estate.   Some folks use small Pixel-type loops with good results.

Mystery Ham

Jim Gilliam

Use a high quality external tuner that has continuous inductor, capacitor adjustments like the Palstar and adjust for maximum noise floor.

Jim, K6QE

Mystery Ham

Al K0VM

The Flex ATU ( and many others) is basically a low-pass filter fucntion.   SIgnals above the matched band are attenuated significantly.  Signals below the matched freqeuncy have very little attenuation.   In practice, actually matching a received signal may increase the amplitude of the received signal AND NOISE, but will not change the signal to noise ratio.  on receive BYPASS will give you all the signal-to-noise your likely to get.

AL, K0VM

Mystery Ham

Mystery Ham

AL K0VM,

But, If manual tuning can get the weak signal on a compromise antenna above the radio's noise floor, you've just accomplished something...

73

WA2SQQ

I might be wrong, but most "auto tuners" use a number of caps and inductors that can be combined in series / parallel combinations using a bank of relays. While this design can simulate an almost infinite combination of inductance and capacitance, it's hardly a "variable" scenario. Since the Flex radios are primarily intended for amateur radio, the development cost and time spent on this feature would not likely do very much to increase the overall sales. The marketing folks might say that "the ROI is very small". Use an outboard tuner - easier and much less expensive. It can be easily connected to the looping connectors. If I had to speculate, this might be something that a user would want if the radio were operated outside the intended amateur bands.

N6OIL

I'll add some gas to the fire,most peeps that are using SDR receive only radios aren't using tuners that I know of. I have a PlaySDR that I just hook up to any of my antennas. But now you have me thinking, when I tune my TS-820S I preselect for the greatest noise with the drive control, so when I get chance I'm going to hookup my external tuner AT-200 to my SDRPlay and see what happens.

Mystery Ham

Mystery Ham

WA2SQQ

At the risk of having this turn into an ongoing debate, I'll make this my last post. Considering the cost of a Flex 6000 radio, I doubt very many SWL'ers are going to purchase one just to listen.  As an SWL'er of more than 50 years an external tuner is much more versatile, and definitely less expensive. As a ham, such a feature would not in any way entice me to buy the radio (for amateur purposes). As a person who works in the consumer electronics industry, I have an extensive amount of knowledge and respect for allocating development resources to any product. You allocate them where you get the biggest return on the investment (time and money). From that point it becomes an issue for the marketing guys to decide. QED

Mystery Ham

Dan -- KC4GO

Regarding reasons to purchase. One of my reasons to purchase the 6500 was because it would also let me use it to do utility and shortwave broadcast listening. Many years ago I purchased a Drake TR-7 for the same reason. The whole world of HF doesn't revolve around Ham Radio.  As for Mystery Ham there are a couple things you can do.
1: Purchase an all band antenna like Comet 250B for RX use, or
2: use a small manual antenna match or per-selector and run it into RX-A.  just watch the pan-adapter for the area of interest to peak.  Check MFJ I wouldn't expect Flex to add the manual adjustment to the ATU.

Rick Hadley - W0FG

In case you missed it, there are now a pair of 6700-R radios on the ISS. I believe that most of us here on the community are unaware, or forget, that amateur radio isn't the only, or maybe even the most lucrative, business that Flex is engaged in, given the opacity of government contracting. When I first got the full dog & pony show at a ham convention, I immediately recognized that I'd have gladly killed someone to get Flex capability when I was working for folks who shall go unnamed, long ago, in a galaxy far away.

Mystery Ham

Dan,

I appreciate your sentiments regarding the HF world not revolving around Ham Radio...  Seems to be an American point of view as most other countries offer shortwave programming along with the ubiquitous possession of shortwave receivers among the citizenry.

From my point of view, part of the beauty of operating a signature series flex is the ability to operate away from the hardware and thus, away from a manual antenna match or pre-selector. Thus the feature request for software based L & C controls when listening out of the Ham Bands.   Call me lazy... 

the comet 250b is interesting but the 15 to 30db hit compared to a tuned dipole or vertical seems a little steep.

Anyway, on the flex tuner, if it is possible to read and write bytes that turn on and off relays to switch in and out inductors and capacitors so the flex hardware automatically memorizes it's prior tune and goes back to it when I change away to another band, tune, and then return, then just maybe the software can manually operate those relays with 2 sliders with values from 0 to 255.  If it's just feeding the tuning processor a frequency and the tuning processor pulls the value from dedicated memory that is inaccessible to anything else, then all bets are off. ( however, I'd bet the Flex folks are keen on diagnostic data and that the registers controlling the tuning relays can be read and manipulated)

Cheers!

Mystery Ham

Reg

Here is a little empirical data on the matter of the role of the tuner regarding received signals.  It was suggested that the tuner will make the signals stronger but it will not improve the signal to noise ratio (SNR).  I performed the following test with my FLEX-6700 using a 160 meter dipole antenna.

1.  I tuned to an inactive portion of the 31 meter band and observed the band noise as -97.1 dBm.

2.  I tuned to a nearby AM broadcast station (6.089,700 MHz) and observed the signal amplitude at -70.1 dBm.

I then switched the antenna output of the FLEX-6700 to a Palstar DL2K dummy load and transmitted with a power of 10 Watts while invoking the internal tuner in the FLEX-6700.*  At this point the FLEX-6700 had performed a "successful" tune at that frequency.

3.  I again measured the inactive portion of the 31 meter band and observed that after "tuning" the band noise was -82.4 dBm.  The noise floor had risen by approximately 8.8 dB.

4.  I tuned to the same nearby AM broadcast station (6.089,700 MHz) and observed the signal amplitude at -61.3 dBm.  The signal strength of the subject broadcast station had increased by 21.1 dB.

Now we do the SNR calculations and we find that they are essentially identical.  It would appear that using a tuner makes the noise floor and the subject signal stronger but the SNR remains about the same.

Reg

* As a MARS member I have an unlocked FLEX-6700 so I can transmit on 6.089,700.  I did not transmit on the air using an antenna.  I transmitted into the above specified dummy load.  Given that I didn't transmit into the receive antenna the match wasn't perfect but it was certainly on frequency.

Mystery Ham

Mystery Ham

N6OIL

Hi MH,
I just heard Joel Hallas give a good talk at the end of his podcast "The Doctor is In" This episode they talked about SDR's and at the Q/A section someone asked about antennas.

Mystery Ham

Thanks for the info...  A internet search a few hours ago took me to the ARRL site, but the podcast hadn't yet been posted.  I'll check later.

Bob G W1GLV

Per Part 97 you are not allowed any RF outside the Amateur Radio bands. Manufacturers are disallowed from providing a means to do this.

Mystery Ham

Kevin K4VD,

Your question about how Flex might handle an antenna match for the 6700-R has me thinking...  It may not be so far fetched if components are modular. The existing board from the 6700 could then be used. However, since transmit power isn't involved, lower cost components that can cover a broader range of mismatches could be used instead...

It appears that the 6000 series already remembers it's prior match settings when switching between bands and locations within a band and puts them into play without transmitting when those frequencies are revisited.  So, once a manual match has been set from the software, things should be in good order as long as the antenna ecosystem doesn't change.

One step farther:

I've never heard of an antenna analyzer requiring a call sign to be input so it can ID itself while it's attached to an antenna. Nor have I seen an analyzer limited to the edges of the ham bands. Perhaps there is some room within the law in various countries to use a momentary low power signal to provide analysis and automatically match an antenna system on an otherwise receive only device.

This may shed some light... http://transition.fcc.gov/ftp/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf

Mystery Ham

Mystery Ham

Bob and Paul,

That is correct, no transmitting required.  Only manual adjustments of L & C via SmartSDR software.

And I believe only one country has a Part 97 rule (law?)   ;-)   Though, I'm confident many countries have something similar but with a different set of requirements.

Though, let me pose a question...  Does that mean an analyzer cannot legally be used in America because it doesn't automatically turn off when you reach the band edges while it's connected to devices or components such as antennas that are designed for frequencies covered by Part 97?

Mystery Ham

G8ZPX

Bob, There is a whole world beyond the North American border where the FCC has no remit.