QRP Power Reference Levels

Many times we refer to power levels for QRP work. For the FT817 and Elecraft Series of KX radios the 5 watt level seems the normal power output

We can use the following as a guide line as a doubling of power is 3dB and vice versa for -3dB

If we use  “dB5W” as the reference, so that 5W = 0dB, 2.5W = -3dB, 10W = +3dB, 50W = +10dB , 100W = +13dB etc.

A calibrated S meter is 6db between positions.

Thus to be at 5 watts of power to be received at S5 will need 12 dB of extra power to be received at S7 or about 80 -100 watts.

Many times with efficient antennas like a dipole one can be heard at S7 which is totally acceptable. To be the Five by Nine (59) or S9 level again the need to increase power by a factor greater than 10 is required.

QRP works more so in CW than SSB where the rule of thumb is voice needs more power than CW operation.

 

SOME THOUGHTS ABOUT NVIS – NVIS isn’t an antenna by KQ6XA 

I presented some radio content at some ham clubs regarding SOTA and NVIS activities. What became apparent that there is confusion because NVIS requires a different antenna configuration (basic dipole 10 feet off the ground) that makes it all confusing? It is not. Read onward please

Bonnie has done a lot of research in NVIS use out in the field.

NVIS

Sat Sep 22, 2018 12:57 pm (PDT) . Posted by:

expeditionradio

SOME THOUGHTS ABOUT NVIS 

The pronunciation of the NVIS initialism as “Enn-Viss” is probably the most common, or else spelled out: “Enn-Vee-Aye-Ess” (N.V.I..S)
I’ve also heard ops say: “Knee -Vuss” and “Nev-Iss”.
Give it some time, someone will call it Knee Vice 🙂

NVIS IS ABOUT FREQUENCY CHOICE 

NVIS: Frequency choice is way way more important than antenna height.

Often, just moving 250 kHz can make a huge difference in NVIS signal.
Commercial and Governmental stations that intentionally utilize NVIS may have a variety of channels to choose from throughout the 2 MHz~13 MHz range.

For hams to take advantage of the NVIS at this point in the solar cycle, operators need frequency agile capability mainly on the following bands:
160 metres 1.8~2 MHz (NVIS Top Band late night when 80m doesn’t work)
80 metres 3.5~3.8 MHz (NVIS evening and some daytime)
75 metres 3.8~4.0 MHz (NVIS evening and daytime)
60 metres 5.3 MHz (Primary NVIS mid-latitude daytime on the Rock Band)
40 metres 7.0~7.3 Mhz (NVIS mid-latitude daytime)
30 metres 10.1 MHz. (NVIS daytime mainly in equatorial latitudes)

EVOLVING NVIS FREQUENCIES AND THE SOLAR CYCLE

Recently, the only daytime NVIS ham bands here in California have been 60 metres and 75 metres… either one or the other… rarely both at the same time.

IONOSONDES AND IONOGRAMS 

Ionosondes capture the critical frequency of the F2 layer of the ionosphere (foF2).
For all practical purposes, we consider the foF2 as “the maximum possible NVIS frequency”.
The foF2 may be different at another location.  Look for the foF2 is the ionosonde that is near your QTH.
https://hamwaves.com/ionograms/en/index.html

ANTENNA HEIGHT 

A dipole at 1/10 wavelength high is a popular misconception and mis-reading of NVIS recommendations for optimum antenna height.

For RECEIVE NVIS, 1/10 wavelength (0.1 wavelength) is the height for optimum SNR (Signal-to-Noise-Ratio) , in a perfect ground site.
For TRANSMIT NVIS, 0.2 wavelength is approximately the optimum height.

There is only a 1dB NVIS advantage at 1/10 wavelength for Receive (compared to 0.2 wavelength).
But, there is a 3dB NVIS advantage for 0.2 wavelength for Transmit.

What this all boils down to, is that 0.2 wavelength is probably the best overall height for an NVIS dipole, above typical (farmland) damp soil.  Over other types of ground, it varies quite a lot.

Generally, the lower the dipole, the more of your transmit power (gain) gets absorbed by the ground soil.

But, with HF receive, the SNR is often more important than gain or loss.
Then, there’s the modern reality of SNR… the RFI received due to nearby RF noise sources.

Whatever height for the receive antenna which achieves the lowest receive RFI, is probably now the best NVIS receive height 🙂
Unless your QTH is totally noise-free, you may need to throw out the NVIS myths about low dipoles being better.

Also, a little-known fact is that a transmitted signal from a dipole, when it goes thru an NVIS path, gets converted to approximately circular polarization by the ionosphere 🙂

See antenna height NVIS chart attached. source: B. Witvliet, 2015
https://ris.utwente.nl/ws/portalfiles/portal/6029527/thesis_B_Witvliet.pdf
In the chart, “hRX” is a good Receive height, and “hTX” is a good Transmit height.

NVIS TECHNIQUES VS HAM TECHNIQUES 

A few things set NVIS somewhat apart from “conventional" HF ham radio techniques:
NVIS can have very short communication distances via ionosphere (less than 150 miles).
NVIS generally has no skip zone.

NVIS uses frequency agility.
+ Strategies that rely on NVIS often use standardized frequencies so the communications path can be tested rapidly and dependably.

Most normal ham radio activity is not really geared for NVIS:
+ Ham nets that are intended to be for a local area, tend to be locked on one frequency.
+ If a station is “too close to be heard”, then someone further away in the net will “relay”.
+ Reluctance to QSY to another band, for equipment, antenna, (hard-headed or lazy) reasons.

LOCAL HF HAM NETS AND NVIS

For example, the NoonTime Net, here on the west coast, meets every day at noon on 40 meters.
It is a wonderful net, usually with hundreds of check-ins when the NVIS frequency is 7 MHz.
But, 40 meters has not been capable of NVIS at noon, most of the time this year, due to changes in the solar cycle.  Most of the time, the NVIS frequency hasn’t been above 5 or 6 MHz.
The “75 meter alternative frequency” for the net has very little activity, even though the local and regional propagation is excellent on it.  The net doesn’t even have a 60 meter alternative frequency, which often would be the best NVIS frequency, and a lot better than 40 meters for the intended net coverage area.

It is noon right now. Looking at the ionogram for this area (attached), it is showing the foF2 optimum NVIS frequency is 4.9 MHz.
There’s no NVIS on 40 meters now, regardless of what type of antenna you have.

The skip distance on 40 meters is around 400 miles at the moment.

“Skip distance” means that you can’t copy anyone closer than 400 miles.

CONCLUSION

NVIS isn’t an antenna.

73s , Bonnie Crystal KQ6XA 

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Icom 7610 Quick Thoughts and Mini Review

Just some quick thoughts

It has more dynamic range than the 7300 and the 756 Pro Series

The two receivers being independent using DigiCell technology is just wonderful

The bigger real estate is great to use in Contests

It is a step up from the 7300 and the Pro series radios

Some trickle down technology form the higher radios 7800, 7851

CW relay chatter is non-existent

CW Audio peak feature is nice (not on the 7300)

A serious operators and those who need reading glasses

Appliance operators will be happy with the 7300 and can save money or go buy a Icom 7100 and a 5100 and a 51A with the difference

Not for the Go Box unless its in a Motor Home

Remember the 11m mod will void your warranty and the RF filters may be tight not allowing much power on 11m but Hey I am not going to try it, I have a Yaesu for that band.

 

 

The Icom 7300 review after 180 Days – Thoughts and Comments

A View of my findings on the Icom 7300 HF SDR Radio

 

  • This is the first Japanese full direct digital sampling SDR based HF radio
  • Radio draws 21 amps at 100 watts output
  • Comes with the standard HM-219 hand mic which provides good audio
  • Direct Digital sampling us used on receive and transmit
  • RF input is through a diode switched bandpass filter – 15 of them
  • The IF is 36 Khz
  • 7300 uses the same DSP chip as the Icom 7100
  • High Stability TXCO is built in 0.5 ppm stability
  • Inside layout is clean
  • Integral heatsink with a quiet fan
  • Multicolor touchscreen display is the big selling point – but I still want knobs for power output and band change. The MULTI offers power out and mic gain.
  • QWERTY keyboard on the display makes memory name super easy
  • I miss the front panel CW key jack
  • Love the 8 pin Din plug for the mic as its better and more reliable than the RJ45
  • SD Card is a great feature and simplifies firmware updates
  • Only 1 antenna jack. I wish they had a receiver jack
  • USB and CI-V port available
  • 99 memories but I wish they had more
  • Notch filter is excellent for those dummies tuning up on nets
  • NR is very good
  • NO CW audio peak filter
  • CW Break IN relay driven but adjustable
  • ATU is still within a 3:1 range because they don’t understand how Elecraft can do 10:1
  • RTTY is cool with 8 pre programmed message stores so one can RTTY like an FT8 robot
  • Spectrum Display – still the selling feature for many. I changed mine to be more useful but I tune up and down but useful for looking at 6 or 10m but really on a busy 20m the display is jammed
  • DVR is nice for voice recording of CQ saving the voice in contests
  • Recording of QSO could be handy
  • Antenna SWR Plot is useful but I prefer a Handheld version
  • Voice Synthesizer a nice touch
  • RS-BA1 software for remote operation but to do it right you need a proper remote ham system set up – ie ability to disconnect antennas , etc
  • OVF tends to flash frequently in QRM sessions with proper antennas but not a problem if you understand how to reduce the input signals
  • No issues running an HF amplifier and the switch times have some adjustment
  • Deaf below 160m as typical but I was supposed on this radio it was provided (   to avoid swamping the FGPA)
  • FAN on all the time during transmit buts its quiet
  • Yaesu FH-2 type keypad missing
  • The 7300 is a fantastic radio and as I continue to read the manual and use it contests and weak signal conditions I realize how useful the new generation of NR, NB and filters can help.
  • Software Update was super easy unlike the nightmare on the Yaesu FT-991

I have Go Boxed this radio for portable ops but have stuck to the Yaesu FT-991 because of the VHF/UHF capability but I find the 7300 to be a better HF radio. Spec wise they are close but the Icom ergonomics are better for my operating style. At least Icom solved the power level knob problem

Excellent work Icom and no wonder over 50,000 units were shipped and even more when everyone had one under their arm at Dayton due to aggressive pricing to keep the bankers happy

So it will be a  while before Icom releases anything to replace it but enjoy it, I cant see the 7400 being that much better as you do need to go to the 7610 and higher for better performance

 

Too bad we dont have the Japanese QRP Version