1. 160 Meter Contests
I operated in both the Fall 2012 ARRL and Stew Perry 160 Meter contests with my new Inverted L Antenna.
With the new antenna I was able to hold a CQ frequency for lengthy periods and many stations called me. This has never happened before.
Also in S&P mode, most often I was heard on my first call even when the calling station was right at my receiver noise level.
In addition I worked the following prefixes: PJ2, C6, XE, KH6, KH8, KL7 and JA's. I even had a JA call
me when I was calling CQ. This never happened before. I called CE/K7CA several times and he came back with VE7? but he was
unable to get the rest of my call.
In addition, several times I heard local hams who run high power (approx. +12 db advantage to my 100 watts) call someone
and make a contact. I would call as well and every time I was also able to make the contact.
My conclusion is that my new 160 meter antenna is working very well.
2. New 160 Meter Transmitting Antenna
I have always enjoyed operating on 160 meters. I built my first homebrew 160 meter transmitter in 1959 with parts
from a discarded TV set. It incorporated a pair of 807's in the final putting out 100 watts.
Over the last 28 years I have tried many different 160 meter antennas. My most recent antenna for top band was an odd shaped 160 meter full wave
length loop. In October 2012 I changed my 160 meter transmitting antenna to an Inverted L with FCP (folded counter poise).
The FCP was developed by K2AV.
I have very little space to lay radials on our city sized lot. Since a vertical (Inverted L) is really a end-fed antenna it requires
some form of path for the return current which typically is either an elevated or buried radial system. A properly constructed FCP
can also serve this purpose within a total length of only 66 feet. Using radials one needs a radius of approximatley 100 feet and
thousands of feet of wire which is not an option at my QTH. I built my FCP over one end of our home at 15 feet above the ground.
The vertical wire is 61 feet and then horizontal for 64 feetwith another 51 feet of wire sloping down at 40 degrees from the end of
the 64 foot length of wire for a total wire length of 176 ft. I am fortunate to have two 90 foot trees on opposite ends of our city size
lot to support wire antennas.
I choose to make the antenna more than a ¼ wave length in order to put the maximum radiating current
near the top of the vertical wire so that maximum radiation is above all the surrounding houses, trees, power line poles etc. The K2AV
FCP is electrically shorter than a ¼ wave length so it requires a series inductance to resonate. The recommended K2AV isolation transformer
has leakage inductance of approximatley 17 uH. Modeling the FCP and Inverted L element total wire length of 176 ft. I determined that 300 Pf
in series with the radiating element would resonate the antenna near 1825 to provide a good match to 50 ohms for my transmitter.
The specifically recommended designed isolation transformer keeps common mode current from radiating from the coax feed line. I purhased
the insolation transformer from Balun Designs, Model 1142s as recommended by K2AV. I measured the 2:1 SWR BW to be 52 KHz and the resonate
frequence is 1830, PERFECT and very close to what EZNEC predicts.
Here is a picture of the LCP isolation transformer and the box containing the 500 PF series capacitor.
For further design information regarding K2AV's FCP, the isolation transfomer please go to: www.w0uce.net/K2AVantenna.html
With my antenna tuner I can tune the inverted L for an acceptable SWR on all bands 80 meters to 30 meters though the radiation angle
would be very high. Good for local contacts.
If you have EZNEC you can download an EZ file of VE7CA's 160 Meter Inverted L/FCP transmitting antenna here.
Click Here
3. Noise:
When I was a teenager, my parents lived on a 5 acre hobby farm and man made noise was not a problem.
Times have changed.
I now live in a city surrounded by power lines and houses containing great assortments of electric devises.
Noise is a constant issue on 160 meters at my QTH. It is the combination of man
made noise coming from multiple sources within the city that cover the weak signals that I want to hear.
In the evening my typical noise level on my 160 Meter transmitting antenna
varies from S5 to S6 until all my neighbours go to bed when the noise level sometimes decreases to
S4 to S5. (Receiver pre-amp off, BW 2.5 KHz, receiver sensitivity -135 dBm).
-Solution No 1: Many years ago I tried to alleviate the noise situation by building a small table mounted
multi-turn coaxial loop which has been featured in the ARRL Antenna Handbook for years. The signal to noise ratio
of the coaxial loop showed a small improvement compared to my transmitting antenna but the ability to null local noise
sources proved to be unsatisfactory. It didn't help that the coaxial loop was in my radio shack which is near the
multiple AC wires in the walls that carrying RFI from many sources in the house., i.e. TV horizontal oscillator harmonics,
microprocessors in various equipment, computers etc. A better solution to my noise situation had to be found.
-Solution No 2: My next step was to move the listening antenna outside. I built a one turn coaxial loop.
It is larger than the table model thus a broader frequency response and does not need to be tuned every 20 KHz.
I mounted the new loop on a 10 foot pipe with an attached rotator so I can turn the antenna from inside my radio
shack. The outside coaxial loop showed a small improvement being it is located farther away from the household noise
sources however like the table mounted loop, the nulls were not as deep as I had hoped for. Experimenting further, I
found that when listening on my coaxial loop, if I grounded the transmitting antenna the noise
level decreased about approximately 6 dB.
If you place a small antenna with a small capture area near a large antenna with a big capture area (both resonant on the
same frequency), the circulating RF current in the small antenna will be overpowered by the RF current circulating in the
large antenna by mutual coupling (which in my case contains significant man made noise). I now short the
transmitting antenna feed-line to ground with a reed relay using the TR circuit in my transceiver. Shorting a near by transmitting
antenna to ground may not work for every situation. You may have to
decouple a near by transmitting antenna (HF Tower) by hanging a 1/4 length wire along side! When I decoupled my transmitting antenna
by grounding the feed line to ground, the coaxial loop showed a significant null in the loop pattern when turning
the coaxial loop to an offending noise source. This is evidence that my near by resonant transmitting antenna
was destroying the coaxial loops radiation pattern by mutual coupling.
Here is a picture of the single turn coaxial loop.
Though the signal to noise ratio of the coaxial loop is sometimes better than the transmitting antenna it has one flaw. It
has two nulls 180 degrees apart. Also the radiation pattern of the coaxial loop does not show any directivity other than
the two nulls 180 degrees opposite to each other. Turning the coaxial loop to reduce a noise source towards the West,
sometimes nulled a signal I want to hear to the East.(depending on the arrival angle of incoming signal). I found that
often when I would null a noise problem I also reduced the signal level of a station I was trying to copy.
-Solution No. 3: A popular low noise receiving antenna used by Low Band operators is the EWE, Flag and K9AY antennas.
These antennas are physically small in terms of wavelength and composed of phased verticals or a terminated
loop. (type in EWE, Flag or K9AY in your search engine and you will find numerous sites devoted to these antennas.)
Properly constructed these antennas are omni-directional and have only one null.
Using EZNEC I designed a small diamond shaped terminated loop. It is mounted on a 12 foot pipe and rotated with a
spare rotator. The diamond loop is supported by fibreglass poles extending 7 feet from the centre
hub thus it has a turning radius of only 7 feet.
Following are the Horizontal and Vertical plots for the Diamond Terminated loop.
If you have EZNEC you can download an EZ file of VE7CA's Low Noise Terminated Loop Click Here
4. Outdoor Terminated Loop Antenna
With the side opposite the feed-point terminated in a 860 ohm resistor, the antenna shows a steep -35 dB when the back is turned
to a local broadcast station at 1750 KHz. Because the loop
is physically small compared to a full sized 160 meter antenna great care must be taken to decouple the
feed-line from the antenna in the balanced versions of these antennas. Generally the antenna looks capacitive
as a common-mode structure, so inductive decoupling (i.e. a choke coil of coax) can actually increase
the system problem. The best common-mode isolation system is an isolated winding transformer
designed with minimal capacitance between the antenna winding and the rest of the system. Also, increasing the
signal level at the feed-point, decoupling beads on the feed line and grounding the shield of the coax close to
the receiver input all play an important role in reducing common-mode problems.
Following is the circuit of a wide band pre-amplifier that I built (taken directly from EMRFD.) It is located at the
feed-point and enclosed in a plastic weather proof box. The amplifier has a gain of +21dB at 1.8 MHz, +18dB at 7 MHz
and zero gain at 60 MHz. A high-pass filter is located between the relay and the amplifier input to attenuate local
broadcast stations. OIP3 is +35 dBm, the noise figure is estimated to be approximately 3-4 dB and the amplifier draws
55 mA’s. I included a relay (operated by the TR circuit in my transmitter) that opens up the terminated loop on transmit.
This reduces the risk of burning out the pre-amplifier by induced high levels of RF from my nearby
transmitting antenna. T1 is two stacked BN-202-73 Amidon cores with 8 T primary and 2 T secondary. T2 is a
FT-37-43, 10 turns bifilar. Power for the pre-amplifier and the relay is via the centre conductor of the coax
feed-line. This antenna is also effective as a receive antenna in the Broadcast band so if you are interested in using
it for Broadcast listening, leave out the high pass filter. Depending upon your own particular situation, if there
are AM Broadcast stations near by, you may still need a broadcast band filter that you can switch in when using the
antenna for 160 or 80 meters.
Pre-amplifier Circuit.
Pre-amplifier mounted and remote control head.
Pre-amplifier mounted in the remote plastic box.
Important: The terminated diamond loop is a balanced antenna and I am feeding it with an unbalanced coaxial feed line.
It is of utmost importance to decouple the coax shield wire from the antenna! The shield must act only as a shield and not
as an antenna allowing pick up of noise along the feed-line otherwise the radiation pattern of the terminated loop will be
compromised. This is called common-mode pick up and is very undesirable. To RF decouple the shield of the coax feedline
I placed 12 ferrite beads, Mix 77, over the RG58u coax feed-line next to the remote pre-amplifier box.
This is often referred to as a current balun. Palomar Engineers sells kits
for this purpose and two sets, Model BA-58, are required for 1.8 MHz. www.Palomar-Engineers.com
Pre-amplifier mounted at the end of one of the fiberglass arms; note location of current balun.
Here is the terminated diamond loop with the VE7CA yagi's in the background.
In order to determine if one antenna is better than another I built a relay operated antenna switch so I
can switch between receive antennas without having to fiddle with coax connetors. I mounted 4 relays in a Hammond aluminum box
with 4 BNC connectors for the receive antennas and another BNC connector for the output. I used decoupling feed
thru capacitors for the control wires which run to a rotary switch on my operating desk.
5. Noise Canceller:
Every 160 meter enthusiast should consider adding a noise canceller to their list of
ham radio equipment. A noise canceller is a device that allows adjustment of the phase and magnitude of an
offending noise source so that it is 180 degrees out of phase with the signal you want to hear thus reducing the level of the
offending signal, (noise or another station). I purchased an ANC-4 Noise Canceller many years ago and have found it a
worth while addition to my ham shack. It is now being sold by Timewave. MFJ also sells a noise canceller,
model number MFJ-1026. See the next section for my comparison of the two units.
A noise canceller can only null noise arriving from one direction. If you have noise
arriving from multiple sources arriving from different directions then a noise canceller will not be of much help. In my
case, my low noise Terminated Diamond Loop has a deep null which I can turn to an offending signal and the noise canceller
can be adjusted to null noise or signals from another direction. It is important to keep in mind that the most effective noise reduction
system is to find and then remove the offending noise.
Previously I had successfully used the ANC-4 on all HF bands from 40 to 10 meters but not on 80 and 160 meters.
The ANC-4 has a “noise antenna gain” adjustment but it does not have enough gain on 160 and 80 meters to boost
the noise from my noise antenna sufficiently (my noise antenna is short for 80 and 160 meters) to be equal to the noise
from my transmitting antenna. In order for a noise canceller to work, the level from the listening antenna and the
level from the noise antenna must be near equal in strength. The overall signal level from the low noise Terminated
Diamond Loop is very close to the signal level arriving from my noise antenna and now the ANC-4 works very well on the
lower HF bands..
Expect to try many different noise antennas before you find one that works for your installation.
My noise antenna is a 40 to 10 meter multi-element wire-dipole located in the West end of the attic of my home.
The Terminated Diamond Loop is at the opposite the end of the house. I have found that I need approximately 1/8 to
1/4 wave length separation between the listening and noise antennas while using a noise canceller otherwise tuning
becomes very touchy or even impossible to adjust for effective noise reduction.
6. Results: The terminated loop in conjunction with the ANC-4 noise canceller has improved my ability to copy many
more stations on 80 and particularly 160 meters.
I have heard a FM5, XE2, P40, LU3, JA and a CE1 station which with the low terminated lopp which were not copialbe with my
transmitting antenna. Comparing the coaxial loop to the terminated loop, if the noise is not in line with the station I am trying to
copy, then the two antennas are nearly equal.
During the evening of September the 25th, 2009 West coast stations were working European stations every few KHz's on the
bottom end of 160 meters. Since W7's and VE7's were giving 599 reports I decided to see
if I could hear any of the European stations with my 160 meter low noise Diamond Terminated Loop
antenna described below. Turning the terminated loop towards Europe and using my ANC-4 noise
canceller I was able to reduce the noise level to near zero on my S meter. Receiving with my transmitting antenna the
noise was S-9. Tuning across the band I was amazed to hear SM5EDX loud and
clear though weak, about S-2. Later I heard OH3HR. I tried to work them both but my 100 watts didn't
make it. My QTH is located on the southern slope of Grouse Mountain (elevation 1,231 m {4,039 ft}). Because of the upward
slope to the north, my antenna is looking into the houses two blocks above my home so I think you can
imagine the difficult position I am faced with trying to work Europe on 160 meters. This was the first
time I have been able to hear European stations on 160 meters from my QTH so if I can hear them, I know that I will eventually
work them.
There are situations where the terminated loop is better than the coaxial loop, especially when listening to DX stations.
My conclusion is the terminated loop is a worthy addition to my amateur radio enjoyment.
7. Noise Canceller Comparisons:
There are many opinions about the effectiveness of the ANC-4 and the MFJ-1026 noise cancellers. Since I
have both, I decided to make side-by-side comparisons measuring and listening to real interference. Because interfering
signals typically are not static, i.e. their signal strength varies over time (QSB) one has to be able to switch very
quickly between the two units to determine if one is better than the other. Removing the coax antenna connectors
from one unit and moving them to the other is not quick enough. So, I built a simple relay switching system that allows,
with the flip of a toggle switch, quick selection of either the ARC-4 or the MFJ-1026.
ARC-4 and MFJ-1650
 |
Switching System
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My observations after switching between the two cancellers, many times over a period of several months while listening to
different types of interference, (steady carries, wobbly computer birdies, noise etc) is that both cancellers are
essentially equal in their ability to null interfering signals. I measured the difference three different ways.
-1. With the AGC enabled I observe the S meter difference between the interfering signal and when it is nulled. Since the
ANC-4 antenna input gain is fixed and the MFJ-1650 is variable I note the S meter reading on the ANC-4 and then match the
MFJ-1650 to the same level. I then adjust both cancelers for the best null. Then switching between the two units I am
able to observe the difference in the null depth.
-2. The second method I measure the difference in the nulling ability with the AGC turned OFF while observing the level on my
scope. With this method, I am able to measure the difference in level between the received interfering signal to the
signal when it is nulled. This elliminates the need to adjust the antenna gain of the MJF-1026 to match that of the ANC-4.
-3. The third method is to listen to interfering signals on my receiver and see if I can hear any difference
between the two units when they are adjusted for maximum interference rejection.
Employing all three methods, I have not been able to descern that one canceller is significanlty better than the other in their
ability to reduce offending signals. With the right combinations of antennas, patience and knowlege very deep nulls
(in excess of 55dB) can be realized with either canceller. The ability to switch quickly between the two units enabled
me to make realistic comparisons between the two units.
It is worth mentioning that the ANC-4 is much easier to tune for a null than the MFJ-1026. As previously mentioned,
one has to first adjust the antenna gain of the MFJ-1026 before you can hear any signals, then tweak the noise antenna gain
and phase and antenna gain controls for the best null. These adjustments are very critical which I found quite frustrating.
With the ANC-4 you simply increase the noise gain while you adjust the noise phase knob for a null.
Once I find a null, I then just adjust the noise gain for optimum noise cancelation.
All the above experiments have been carried out on the lower HF bands with my particular noise antenna in
combination with the Low Noise Terminated loop. I must stress that every installation is different
from another and there are many many variables between installations. You may obtain different
results using your particular antennas. There have been instances where I can obtain a good null with the ANC-4 and not the
MFJ-1026 and vis-versa for which I have no explaination.
Here is a copy of an email from Tadek, SP7HT regarding his experience with the ANC-4/MFJ-1026 plus information
regarding modifications he made to his ANC-4.
"For years I am competing with local noises using ANC-4 (firstly) and MFJ-1026 (last 10 months) for noise cancelling.
I've modified the Front End of my old ANC-4 adding a tuned resonant circuit at the Input of Noise Channel (low impedance
Input to resonant circuit, next High impedance paralell resonance circuit using ferrite core and RX tuning capacitor I can
cover in 4 sub-bands from 1.74MHz to 30.1MHz and at the output low impedance to connect directly to ANC-4 noise antenna
Input socket).
At the Output of that modification (outside ANC-4 case) I can adjust the level of noise signal (470 Ohm potentiometer)
connected to ANC-4. So, I can adjust NOISE GAIN in the middle position, when best cancelling can be reached (in ANC-4).
Thanks to selective resonance circuit at the Input of Noise antenna I can avoid intermodulation products when propagation
is in a great shape (birdies appeard every 5kHz or every 10kHz).
According to local noises in my location (a 5 floor block of flats, 19 neighbours in that house and about 300 neighbours
in 100 metres circle around my location) I can say (today) that my modified ANC-4 is an exellant tool to fight with local
noises"
Tadek's addition of a variable pot (attenuator) at the Noise Antenna input is a good addition to the ANC-4 if you
are using a noise antenna that has more gain than your receive antenna such as a EWE, Flag, K9AY or Terminated Loop.
An attenuator at the noise antenna input provides a wider range of control of the noise level allowing a closer
match to the two antenna input levels.
