PSK Splatter solved

While operating PSK on 20m this morning I received a report that I was splattering across the band. With this in mind I though I should look into this.

I was not operating outside my normal situation.

FT2000D
30W - 80W depending on the QSO
Signallink USB
HP PC
only have 1 antenna, the Windom

Let the experiment begin.

Not knowing how bad the problem was, I went up to 18.1MHz to find a quiet place to poke around.

The only station I saw on the band was a fellow operator here in Ottawa, VE3OIJ. We transmitted back and forth a bit and found nothing remarkable. Leading me to think nothing is seriously broken.

I wanted to see my own signal, so I used the IC7000 to receive the tx output of the FT2000D

Rig
TRX - FT2000D
Freq - 18.1MHZ
Tx Power - 50W (by the FT2000D meter)
PSK Tones - 600Hz

SignalLink
Tx - 3/10

Measurements - HRD on IC7000
Signal S9+20 (input to IC7000 grounded at antenna switch)
IMD - 19dB
SNR - 19dB

Fundamentals 600Hz @ -20dB
Spurs @ 1800Hz @ -70dB 3rd Harmonic
"Image" @ 2900Hz @ -80dB 5th Harmonic
Spurs @ 3300Hz @ -80dB ??

At 6dB/S-unit, if my fundamental was received at his station at S9, then this "splatter" would be received at -S2, i.e. 2 S-units below, S0, these cannot possibly be the splatter my fellow operator saw.


VE3OIJ was able to see these terms, but we are less than 10km apart. It may make sense to follow these terms a bit more. The plot below shows my signal from 1W to 150W into my dummy load. In all cases the relative size of the "splatter" remained fixed. This tells me that these terms are not being generated by the radio's linearity ans regardless of my transmit power would not be a problem to any one but an operator in my city.


How to get gid of these? Don't know.

Next step was to try back on frequency, in case it was RF feedback into the shack that only happens on 20m.

Rig
TRX - FT2000D
Freq - 14.070MHZ
Tx Power - 50W (by the FT2000D meter)
PSK Tones - 600Hz

SignalLink
Tx - 3/10

Measurements - HRD on IC7000
Signal S9+20 (input to IC7000 grounded at antenna switch)
IMD - 19dB
SNR - 19dB

Fundamentals 600Hz @ -20dB
Spurs @ 1800Hz @ -70dB 3rd Harmonic
"Image" @ 2900Hz @ -80dB 5th Harmonic
Spurs @ 3300Hz @ -80dB ??


Identical results.

Below is a typical waterfall on 20m, "strong" signals are 30dB above the noise floor. If anyone else had terms like the ones above in their transmit signals there is no way I would ever see or be concerned with them.



Summary

I cannot improve the relative power in these terms by adjusting my TX power, as they go dB for dB with my fundamental signal.

Only someone in my local area will see these signals as significant, and the operator who indicated I was splattering did not leave his call so I can not tell. I should has asked, but I did not, a short QSO may have been a better idea.

For now I'll assume every thing is ok and go back to having fun.

Update:

Here is another plot of my tx signal.


Update #2

I was in a QSO with a Spanish station and received a 575 report, so again I thought something must be wrong. A plot of my transmit signal is below.

This time I recognized that the "regrowth" was at N times 120Hz, pointing me to a power problem. Also, I though I'd take a look at my CW output as a means to remove the PSK hardware and software from the equation. Below is my CW plot, this was for 10W output.


In my shack I power my table from two power bars. One regular power bar for all the ordinary stuff, PC, lamp, monitors, and a filtered power bar for the FT2000D, DMU2000, and the Kenwood PS-53 for the IC-7000 and / or TS-850. Both power bars are powered from the same wall outlet which has a dedicated 15A circuit for the sta

I can see in the plot above, that the same N*120Hz side tones are present, the first pair are only 35dB down.

Below is a plot of the same CW transmission when the FT2000D + DMU2000 and Kenwood PS-53 supply are on the same power bar as the rest of the shack. (avoiding the MFJ power

I can see in the plot below, that only the first 120Hz side tones are present, but now are 60dB down, a 25dB improvement. The MFJ-1164B power bar will need some further investigation.


In the meantime, returning to PSK mode, below shows a much improved transmit signal.

Rig
TRX - FT2000D
Freq - 18.10MHZ
Tx Power - 130W (by the FT2000D meter, just for testing)

Excellent.



Now I think I have a very good idea of how clean the PSK signal should be from my radio and will keep an eye.

Summary:

1) If you have an extra radio and Signallink you can run 2 copies of DM780 and see your own transmit signal. Grounding the second rig's antenna input will enable enough signal in to be detected.

2) Your AC supply should be suspected if you have N*120Hz sidebands

3) Read an understand how volume controls should be set for your software and PSK interface hardware

4) Looking at your CW output can help isolate the problem

5) a good transmit signal will have better than 25dB IMD, better than 25dB SNR and 60 to 70dB spurious free range.

All for now.

Safety Code 6

As a licensed amateur radio operator in Canada this is my personal interpretation of Safety Code 6. I am presenting this here for any like minded amateur radio operator who is interested in this topic.

Regulations

The Radiocommunications and Broadcasting Regulatory Branch of Industry Canada states in "CPC-2-0-03 Radiocommunication and Broadcasting Antenna Systems" (link) that Health Canada has established safety guidelines for exposure to radio frequency fields, in its "Safety Code 6" (link) publication.

"Safety Code 6" states that current studies in Canada and other countries indicate that there is no evidence that a person will experience adverse health effects from exposure to radio frequency fields, provided that the installation complies with Safety Code 6.

It is my responsibility that my amateur radio station comply with Safety Code 6 at all times.

Safety Code 6

Safety Code 6 recommends general procedures for ensuring that exposure of the general public in the vicinity of RF devices is not greater than the levels specified in this Code. A safety factor of approximately 20 to 50 was incorporated with reference to the scientific-consensus threshold for adverse health effects.

Field Strength Limits (Source Safety Code 6)

Within the 3 to 30MHz bands, a person shall not be exposed to electromagnetic radiation in a frequency band listed in Column 1 of Table 5, if the field strength exceeds the value given in Column 2 or 3 of Table 5, when averaged spatially and over time. The spatial averaging is carried out over an area equivalent to the vertical cross-section of the human body (projected area). A time-averaging period of 0.1 h (6 min) should be employed for frequencies up to 15 000 MHz.

src: Safety Code 6

Canada's National Amateur Radio Society (link)

States that while Industry Canada expects radio amateurs to meet the requirements of Safety Code 6, generally most amateur installations will never exceed the recommended exposure limits. There are many reasons for this including the fact that most amateur installations are operated at relatively low power levels (typically 100 watts), are not on a 100% continuous duty cycle and the amount of transmission time is often limited."

Interpretation

From Table 5

From 1 to 10MHz, Electric field strength is limited to 280/f (V/m) and Magnetic field strength to 2.19/f (A/m).

From 10 to 30MHz, Electric field strength is limited to 28 (V/m) and Magnetic field strength to 2.19/f (A/m).

For each band from 80m to 10m the table below captures the E and H field limits according to the safety code 6 definitions.

I assume 200W output from my rig, which is worst case. 100ft of feed line is assumed with 1.3dB/100ft at 30MHz. To get the losses at other frequencies I scaled the loss by the frequency of each band. I assumed a 3dBi antenna gain which is correct for the Cushcraft R8 Vertical. Effective radiated power is 380W to 290W.

Power density is calculated assuming a worst case 3m distance to the antenna.

For PSK modulation I assumed a 50% time averaging over 6 minutes which is consistent with PSK operation, as I listen 50% of the time, and a typical transmission is much less than 6 minutes. On the other hand I assume duty cycle of 100% when I am transmitting. This factor would be less than 100% for SSB and CW for instance.

Operating Mode	Duty Factor
Morse code (CW)	40%
SSB phone	20%
FM	100%
RTTY/Digital	100%
AM	100%

source: http://n5xu.ece.utexas.edu/rfsafety/power.shtml

I then calculated the resulting averaged E and H field strengths.

Simply taking the ratio of the resulting field strengths and the limits results in a safety margin over and above Safety Code 6.

A copy of this file is available at Google Docs at link.

Limits
Band	(m)	80	40	30	20	17	15	12	10
Freq	(MHz)	4	8	10	15	18	20	25	30
E Field Limit	(V/m)	75	37	28	28	28	28	28	28
H Field Limit	(A/m)	0.58	0.29	0.22	0.15	0.12	0.11	0.09	0.07
Transmitter and Antenna
Output Power	(W)	200	200	200	200	200	200	200	200
Feed line	(ft)	100	100	100	100	100	100	100	100
Feed line Loss	(dB)	0.2	0.3	0.4	0.7	0.8	0.9	1.1	1.3
Antenna Gain	(dBi)	3	3	3	3	3	3	3	3
Effective Radiated Power	(W)	384	370	361	344	335	327	311	296
Density
Distance to Antenna	(m)	3	3	3	3	3	3	3	3
Power Density	(W/m^2)	3.40	3.27	3.19	3.04	2.96	2.89	2.75	2.62
Averaging (PSK-31)
Time averaging		50%	50%	50%	50%	50%	50%	50%	50%
Modulation		100%	100%	100%	100%	100%	100%	100%	100%
Resulting Fields
E Field from antenna	(V/m)	25	25	25	24	24	23	23	22
H Field from antenna	(A/m)	0.07	0.07	0.07	0.06	0.06	0.06	0.06	0.06
Safety Factor
E Field		2.9	1.5	1.1	1.2	1.2	1.2	1.2	1.3
H Field		8.7	4.4	3.4	2.3	2.0	1.8	1.5	1.2
Feedline	dB/100ft	1.3
	MHz	30

Conclusion:

I would state that a Cushcraft R8 vertical at 3m, being fed with a with Rig power of 200W in PSK mode and 100ft of feed line will pass safety code 6.

There are details concerning the Safety Code 6 in the near field which I have not reconciled.

I believe the calculation above to be correct, however all should realize you are accountable for your own calculation, should you attempt to do one for your own station.

Buddipole 4NEC2 Model Files

I have found a way to post my 4NEC2 Buddipole modeling files on line using Google Documents.

Eventually I will log many of my design files here for anyone to use.

4NEC2 is available at http://home.ict.nl/~arivoors/

Below is a list of the files I have created.

FILE AC_Vbud_40M_09_V01 40m Vertical, (longwhip, 4 dipole arms, red coil)
FILE AC_Vbud_40M_08_V01 40m Vertical, (longwhip, red coil, 4 dipole arms)

Detailed Files:

FILE AC_Vbud_40M_09_V01

Description, LongWhip with RedCoil and 4 Dipole Arms on VersaTee w/ TRSB set to 25ohms (2:1) and 1 8.6m Counterpoise.

This is a new configuration
a) attempting to generate a lower takeoff angle and more gain
b) 40m PSK31 frequency (7.07MHz)
c) Red coil was moved to below the arms and whip
d) Suggested by Ray (K7RFW)

1 fully extended Long Whip
4 22" Dipole Arms
1 RedCoil tapped turns from Bottom
1 Versatee
1 TRSB,(2:1) 25 ohms
1 8.6 (m) Counterpoise

Takeoff angle	30	degrees
Gain	0.0	dBi
SWR	1.6	into 25 ohms

Conclusion:
Moving the red coil to below the dipole arms, resulted in a modest loss of antenna gain from 0.6dBi to 0dBi, the take off angle remained the same at about 30degrees. The inductance needed to maintain the antenna at resonance (7.07MHz) was reduced from 15uH (18 turns form the bottom) to 10uH (25 turns from the bottom). Best case SWR was increased from 1.1 to 1.6 as the impedance of the antenna decreased from 22.5ohms to 15.6ohms.

Overall, I would take from this, that is it better to not have the coil placed adjacent to the feed point.

-------------------------------------------------------------------------------------

FILE AC_Vbud_40M_08_V01

Description, LongWhip with RedCoil and 4 Dipole Arms on Versatee w/ TRSB set to 25ohms (2:1) and 1 8.6m Counterpoise.

This is a new configuration
a) attempting to generate a lower takeoff angle and more gain
b) 40m PSK31 frequency (7.07MHz)

1 fully extended Long Whip
1 RedCoil tapped 18 turns from Bottom
4 22" Dipole Arms
1 Versatee
1 TRSB,(2:1) 25 ohms
1 8.6 (m) Counterpoise

Takeoff angle	30	degrees
Gain	0.63	dBi
SWR	1.11	into 25 ohms

-------------------------------------------------------------------------------------

Special QSL Cards

Two new QSL cards will be on their way.

For the winter camping "DX-pedition" I made up the card below, it shows the Yurt, and the cozy operating station inside. The globe was generated from Google Earth through Ham Radio Deluxe and the IC7000 radio image complete card.


I've been running the call GC3IAC since the beginning of February in celebration of The International Year of Astronomy. The special prefix call sign starts 1 Jan 09 and ends 27 Feb09 23:59 UTC

VE changes to CG, VA changes to CF, VO changes to CH, and VY changes to CI



I have not posted these in the mail but I will in the next few weeks.

73

Winter Portable Operation

This post is related to a winter weekend trip to Silent Lake where my wife and shared some quiet time and I was also able to operate portable.

Silent lake Provincial Park is one of a few provincial parks in Ontario which have winter camping facilities. It is located in central Ontario and is a 3.5hr drive west from Ottawa. We arrived at the park office at about 9:30AM where we were greeted by the Park Warden and were taken to our Yurt by skidoo and trailer. The temperature was -25C when we arrived, and although it warmed up a bit during the day it remained very cold.

The Yurt we stayed in was a simple and basic structure, as expected, equipped with plenty of firewood, a good axe, and a wood stove for heating. Two bunks provide room to sleep 6.


I setup the buddipole vertical in a new configuration, I replaced the standard stainless steel whip with a long whip.

The vertical was built as

• Long Whip (fully extended)
  
• Red Coil (tapped 13 from the bottom)
  
• Dipole Arm
• Wersatee
  
• 1 28.5ft Counterpoise
• TRSB set to 2:1 (for a 25ohm antenna)
  
• Feedpoint about 2m from the ground

I simulated this configuration with 4NEC2 and predicted it should resonate at 7.1MHz.

The radiation pattern was also predicted as below.


The file for this 4NEC2 is archived in the Yahoo Buddipole group in the folder
(See file : AC_Vbud_40M_07_V01)

This tuned up at 1:1 SWR on my IC7000 just as predicted.

Since the Yurt has no electricity, my operating station was powered by 4 50AH Gell-cells and a N8XJK battery booster. The laptop was also powered off of the same cells. I operated for 5hrs and the 4 cells were depleted to 70% capacity.



Most of my operating was in the evening and by candle light. The small wood stove needed attention once and a while.




From 20:45UTC to 3:00UTC I was able to complete 15 PSK31 QSOs and I want to thank everyone who I was able to contact. You can see my log below.


Google Earth export shows just how far 50W and a Buddipole can throw a signal. I was very pleased by the following QSO's in particular.


EA8CFV 559 599 Padron Eligio 281 5,469.59 IL18tl Spain

P40PZ 599 579 Peter 91 3,675.83 FK42xo Aruba

W6TJK 559 599 Thomas J Kenville 291 3,931.85 CM87xb United States of America

XE1YK 599 599 CARLOS EDUARDO LEVY VAZQUEZ 50 3,610.25 EK09jh Mexico

K3ML 559 589 MILFORD C GOSSARD 291 2,348.95 EL94gq United States of America

K4WNY 559 599 RONALD S TURNER 291 1,626.32 EM55ak United States of America

VA3SQ 599 599 John D Sibbett 1 378.47 FN02jx Canada

Special note and thanks to Peter P40PZ in Aruba, as this QSO was my first to DXCC country 91.

Thanks

Adrien

...

Mark's post from an earlier trip

Buddipole

I have been experimenting with using a Buddipole for portable operations. Details on the Buddipole can be found at this link.

One configuration that is interesting is the 40m vertical as described in the Buddipole document at this link. I have used this and it tunes up very nicely, but I was also interested in seeing if I could model this configuration and possible find another more efficient configuration using other components.

I loaded a copy of 4NEC2 and generated a few simple antennas, dipole, Inverted Vee, and a vertical.


Model 1: Basic 40m Vertical w/ 1 counterpoise

Setup is Versatee + Dipole Arm + Red Coil + Short Whip and 1 counterpoise. I use the TRSB at 1:1 setting.


Key parameters: With the help of Dave KI6AWR, I am using a 28.2uH for the red coil.



This prediction of this antenna can be made to resonate at 7.07MHz but the SWR of 3.4 is worse than I had observed in reality.


This configuration has the following predicted values

Resonant frequency: 7.07MHz
SWR: 3.45

Model 2: Extended 40m Vertical w/ 1 counterpoise

Setup is Versatee +Red Coil + Dipole Arm 1 + Dipole Arm 2 + Long Whip and 1 counterpoise.


In this configuration there the vertical is 1.4m longer due to the second dipole arm and the longer length of the long whip. Also the red coil has been placed at the bottom of the vertical. The counterpoise is unchanged, and the loading coil is tapped at 49% of its full value. (this returns the antenna to resonance at 7.07MHz.



There is expected to be 1.4dB more gain at the same takeoff angle of 50degrees.



It should be possible to use a long whip and both dipole arms to extend the vertical. A bit more gain is expected and the red coil is expected to be at to 49% (20 of 41 turns) to compensate for the longer antenna. The counterpoise length does not need to be adjusted.

End Notes:

a) I am unsure why the predicted SWRs are so high. I was expecting better than 2:1.

Noise, The Hunt for RFI

I posted earlier that I have decided that I have power line radio frequency interference which is obstructing my amateur radio reception. The task now has turned to isolating the source.


Step 1. Isolate if source is in my house.

I set a battery powered SW radio to AM mode and tuned it to a frequency in the 80m band where the noise was particularly undeniable. Then I went to the breaker panel in the house and turning off the MAIN circuit breaker.

No luck, The noise level at 3630MHz was at Signal Strength 5 with or without power in the house.


Step 2. What Next?

Directional antenna? and What band?

These are not independent. A directional antenna can be used but only on VHF, and VHF also requires the noise source to be close by. For example a 440MHz Beam and a 440MHz hand held AM mode would do the trick. Examples are captured below I will have to decide if I need to go this route.

Cushcraft A4496S 6 Element 440MHz Amateur Radio Antenna


The Cushcraft A449 6S is an effective, economical choice for your 70 cm FM/Packet needs. Great for vertical or horizontal polarization configurations. Mast shown is not included.

Specifications:

• * 3dB Beamwidth, Degrees E-Plane 60
• * Boom Lenght ft.(m) 2.9(0.89)
• * Forward Gain, dBi 10.5
• * Frequency, MHz 440-450
• * Front to Back Ratio, dB 18

Yaesu VX-7R Tri Band Handheld Amateur Radio Transceiver


Yaesu VX-7R Tri Band Handheld Amateur Radio Transceiver is a triple band (6M, 2M & 440 MHz) HT with extensive receive coverage, and leading-edge features. Power output on 6 meters, 2 meters and 440 MHz is 5/2.5/1/0.5 Watts. It receives the AM and FM broadcast bands, shortwave (AM), VHF and UHF TV audio, VHF Air and public service frequencies.

Features:

• * Receiver coverage 500 KHz to 999 MHz (Cell Blocked)

Step 3. AM Radio from the Truck.

I decided to give the radio in the truck a try. I tuned the AM radio to 1700kHz, the very top of the AM broadcast band. Then proceeded to take a drive around the neighborhood.

My drive route took me past several locations where I thought I may find my noise source; street light standards, the well lighted neighborhood grocery parking lot, several hydro electricity transformers, (the neighborhood has under ground electrical distribution).

What I found was very odd.

There were a few highly localized hot spots quite far from my house.

One was on a housed street about 500m from home, the noise source had the typical 120Hz sounding signature but the source was very localized, as it only presented it self over a <20m class="blsp-spelling-corrected" id="SPELLING_ERROR_11">noise was remarkable strong was; (in descending order)

• In my next door neighbor's driveway
• In my own garage
• In my other next door neighbor's driveway

more to come...