Station Components | Audio Chain | Audio Settings | Antenna | Links
Amateur Radio has been a wonderful hobby for me for many years! I especially enjoy the opportunity to build meaningful friendships with other hams. I became a licensed ham in 1972 to facilitate telephone patch calls to my wife Pat from aboard ship in the Pacific during my 28 year Navy career. I was fortunate to operate my own equipment (Kenwood TS-520 and trap vertical) from five Navy ships.
Components are described below:
Dell Studio XPS Desktop 435 MT and 24 inch monitor.
- 640GB, S2, 7.2K Western Digital, XL320 hard drive
- Intel I7-920, 2.66, 8MB
- Running 64 bit Windows 7 together with Ham Radio Deluxe for rig control, logging and digital ops. DB9 serial cable interface to TS-870 via separately installed serial pci express card described at http://www.usconverters.com/index.php?main_page=product_info&cPath=69&products_id=248 together with RigBlaster audio interface.
- Skype ( user name donsno ) together with MS Life Cam Cinema as described at http://www.microsoft.com/hardware/digitalcommunication/productdetails.aspx?pid=008 .
Kenwood TS-870 with matching SP- 31 matching speaker and PS-52 power supply (not shown)
Palstar AT1500BAL balanced line antenna tuner
Ameritron AL-80B linear amplifier.
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Notes:
(1) All audio is routed via 3 conductor shielded XLR cable.
(2) The audio output from the DEQ 2496 audio processor is routed directly to the microphone input jack on the TS-870. I adjust "gain offset" of the DEQ- 2496 as necessary (about -10) to help reduce line level audio output to something closer to microphone levels expected by the microphone input stage of the TS-870. Alternatively, I have sometimes used e a W2IHY iBox to match line level to microphone level, audio isolate and impedance match.
(3) A "common point" rf ground system, although a good practice, is not essential to minimize the likelihood of rfi.
(4) A Daiwa SWR/Wattmeter is inserted between the linear amp and balanced line antenna tuner.
(5) PR-35 low end roll-off switch in the -3dB position.
Audio components:
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Boom mounted Heil PR-35 dynamic microphone. You can read a review and comparison of this microphone and others by clicking microphone review. "Michael", our Bengal Snow Leopard, thinks he is the station manager. :>) Alternatively, an ElectroVoice Blue Cardinal pressure-gradient cardioid condenser microphone is sometimes used.
Kenwood TS-870 and matching power supply above a rack mounted Behringer MIC2200 Microphone Preamp and DEQ2496 Digital Audio Processor.
Current settings on the MIC2200 Microphone Preamp:
- Phantom power off (except when using the ElectroVoice Blue Cardinal)
- Phase Reverse button off
- Input gain +35db
- Cut on and set to 50Hz
- Parametric EQ on, frequency 160Hz, band width .96 and level of -12 db
- Output +4db
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Current settings on the DEQ2496 Digital Audio Processor:
GEQ (Graphic EQ) and Limiter- Bypassed
PEQ (Parametric EQ) - Five filters as follows:
Note: The Kenwood 870's TXEQ is kept in the "off" position and TX bandwidth is set at 3K for both transceivers. TX shift is 100. The PR-35 microphone low end roll off switch is at position 3.
DYN (Dynamics processor) settings for the Downward Expander, acting as a noise gate. Gain is initially set to 0 db, ratio 1:1.8, attack 0.00ms and release 85.6ms. The threshold and ratio controls are adjusted until room noise diminishes to the desired point. The compressor capability of the DYN is not currently being utilized in favor of the DEQ as discussed below. Note: I have been able to avoid the necessity to use the DYN by keeping ambient shack noise to a minimum and close talking the microphone.
DEQ (Dynamics EQ) has three separate DEQ's available. Each one has 3 pages of parameters. DEQ 1 is configured for low frequency compression, DEQ 2 for midrange compression and DEQ 3 for high frequency compression as follows:
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DEQ (Channel R)
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Page 1
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Page 2
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Page 3
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1 (low)
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M-Gain: -15.0
* Threshold: -40
Ratio: 1:20
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Attack: 2.77
Threshold: -40
Release: 105.4
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Mode: BP
Freq: 90.4
BW (oct): 3
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2 (mid)
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M-Gain: -15.0
** Threshold: -45
Ratio: 1:20
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Attack: 0.70
Threshold: -45
Release: 50.9
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Mode: BP
Freq: 1002
BW (oct): 3
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3 (high)
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M-Gain: -15.0
*** Threshold: -49
Ratio: 1:20
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Attack: 0.70
Threshold: -49
Release: 20
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Mode: BP
Freq: 4035
BW (oct): 3
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* adjust threshold as necessary to attain about -4 gain reduction.
** adjust threshold as necessary to attain about -5 gain reduction on voice peaks.
*** adjust threshold as necessary to attain clean "S" ing sound.
Note: The above settings work equally well with both the Kenwood TS-870 and the TS-2000. The DEQ2496 is being run with default settings in the "Utility" menu except for Channel mode" which is set to "stereo" and "Gain offset" which is set to +3.0 as makeup gain to partially compensate for some negative PEQ settings. DEQ2496 Input levels adjusted (output level of the preamp) to obtain peak meter reading -15db, RMS -21.5. The GEQ, DYN and Limiter are bypassed in both channels.
The above graph of received audio is courtesy of ZF1DG "Durl" recorded during a 20 meter QSO on 5/27/2010 . Note the comparison between a transmit bandwidth of 3K as compared to 2.6K. I typically maintain 2.6k which yields nearly identical perceived audio quality while occupying less bandwidth than 3k.
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The antenna
This 10 - 160 meter tuned horizontal loop antenna is fed with 450 ohm ladder line all the way into the ham shack to an Palstar AT1500BAL balanced line antenna tuner. The above graphic depicts the overall layout of the loop antenna consisting of 558 ft. of #16 "silky" stranded wire cut to one wavelength long on the lowest operating frequency (160 meters). The mean height of the loop above ground is about 55 ft. The loop is suspended from from four corners by nylon halyard strong over the top of 4 adjacent trees as shown above.
- Side A is 40 ft
- Side B is 208 ft
- Side C is 55 ft
- Side D is 255 ft
- Side E consists of about 65 ft of 450 ohm ladder line running from the tuner in the shack to the antennas feed point which is about 55 ft above ground level.
Note: Click 80 meter loop for a sketch of a similarly constructed 10 - 80 meter delta loop that has sometimes been in operation.
A - Method used to bring 450 ohm feed line into the shack consisting of a painted 1 x 6 board cut to the window's width. The feed line passes through a slot. Clear silicon sealant was used throughout.
B - One of four corner loop suspension points consisting of nylon pulley attached to nylon halyard.
C - Loop antenna feed point. 'Silky' 16 AWG, 19 strand, tinned, 40% copper-clad steel forms the loop itself and 450 ohm, 16AWG, 19 strand copper-clad steel conductors, poly-clad "window" is used as the feed line.
Why choose a loop antenna?
Loops are usually cut a full wavelength long on the lowest expected operating frequency. The formula for a full wave loop antenna is Length (feet) = 1005/f MHz. For example, a loop for the frequency of 3.800 MHz would be calculated as follows: 1005/3.8 = 264 feet.
A multi-band loop antenna offers significant advantages especially for hams who prefer to only use one wire antenna for all bands:
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A loop is quite forgiving and perfect symmetry is not essential. Ideally the loop should be be in a configuration providing the greatest enclosed area at the highest height possible. Since the loop can be erected in unusual places and still perform well, treetop suspension is often used. I rely on heavy duty nylon or black dacron halyards with nylon pulleys at each attachment point to keep equal strain on each leg of the loop. A slingshot, fishing line and heavy sinker get the halyards up and over the trees as necessary.
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Unlike a center fed dipole, the loop can be fed at any convenient point.
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Since the design of a loop is typically a square or delta form, the need for a long straight run of wire such as a dipole is diminished.
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A loop makes for an efficient broadband radiator, even when low to the ground or close to obstructions such as tree limbs. The majority of the amateur bands are harmonically related, typically the 1st harmonic. A loop is easily tuned to resonance on all harmonics of its fundamental frequency. A dipole by contrast is easily tuned to resonance only on its odd harmonics. A loop starts out with 1.2 dB of gain over a dipole on its fundamental frequency.
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A loop's gain over a resonant dipole increases with the increasing frequency of operation. Therefore, when used on its harmonics, a loop's signal advantage over a dipole likewise increases. At higher bands, radiation angle is lowered resulting in improved DX performance.
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The venerable loop is easy for a balanced line capable tuner to match on all bands when fed with 300 or 450 ohm balanced feed lines.
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Although I'm not convinced, most hams who use loops often claim that a loop is less susceptible to atmospheric and man-made noise.
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Ladder line fed loops significantly reduce the chances of rfi in the shack. The antenna does not rely on the need for a good RF ground to the same extent as unbalanced coax fed dipoles or loops. There is widespread misconception on this point. More about this below...
Many hams find it difficult to bring ladder line all the way into the shack to the tuner and resort to the use of remotely located coax fed balun (usually 4:1) connected to the ladder line. I have tried this approach and found that it usually works better on some bands than others. My recommendation is to avoid this technique if at all possible. Finally, try to use a tuner design that has been optimized for this type of antenna.
You too may want to consider the time-honored loop. It is simple and inexpensive to homebrew and can yield surprisingly effective performance. All things considered, it's a great multi-band antenna.
visit http://www.cebik.com for a theoretical examination of the effectiveness of large loop antennas.
Why feed the loop with balanced line?
If you doubt the viability of feeding wire antennas like loops and dipoles with open wire line, read the following explanation courtesy of K5UA "Charles":
There are two kinds of line loss, the matched line loss and the mismatch line loss. Matched line loss is measured at different frequencies in db per 100 feet when the line is terminated into a load which is identical to the characteristic impedance of the line. The loss increases as the frequency increases.Mismatched line loss is an additional attenuation of the signal because of the line being terminated into a load which is different than the characteristic impedance of the line. This loss increases with frequency, but it also increases with the magnitude of the mismatch. Needless to say, lossy lines like the small coax have higher mismatched line loss numbers for the same amount of mismatch than the lower loss, large coax lines.
Matched line loss is unavoidable, but mismatched line loss is avoidable if the load can be matched to the line at the load end of the line. An example of this would be a gamma match at the yagi terminals to transform the 16 ohm impedance of the antenna to the 50 ohm characteristic impedance of the coax. Another example would be to use a 4:1 Balun at the antenna terminals to bring the 16 ohms closer to 50 ohms.
The match can also occur at the transmitter end of the line, but the mismatched line loss would be there. The transmitter would be happy looking into a 50 ohm load, but the mismatched line loss would still be present because the load is not matched.
The beauty of open wire line is that the matched line loss is virtually zero. Even with large line/load mismatches, like 10:1 or 15:1, the additional mismatched line loss is very low. As long as the user has a conjugate match on the transmitter end of line using an antenna matching network, virtually ALL power is radiated by the antenna. Power can not disappear, it is either radiated or lost in the line by attenuation of the dielectric material between the transmission line wires. This is why a random wire of reasonable length may actually radiate MORE power when fed
by open-wire line through a tuner, than a perfectly matched half-wave dipole fed with small coax, assuming the feed line length of each is over 100 feet.
The net effect of this is that you can put up a random length dipole (or a loop as discussed here) and use it on all bands with very little line loss and not have to worry about a bunch or resonant dipoles interfering with each other.
K5UA, in another email, goes on to say:
The probability that any single element antenna is going to have a feed point impedance of 50 +/- j0 ohms is virtually ZERO.
Likewise, when I hear of someone bragging about their quad or yagi that is 50 ohms at resonance, I always ask them how much gain and front to back did they have to sacrifice to get that 50 ohm feed point impedance. Apparently when God was designing the universe and the laws of physics, he did not realize that the tail (50 ohm coax) was going to wag the dog (gain/front-to-back/multi-band operation) in the antenna world.
The concept of resonance also appear to baffle most amateurs because they do not know or understand the three components of impedance (resistance, inductive reactance, and capacitive reactance). A lot of amateurs believe that resonance occurs only when the antenna impedance has the same 50 ohm resistive component as the coax impedance. Actually, resonance is simply defined as the absence of the reactive component of impedance, or in other words, a purely resistive load. If the impedance of a resonant dipole is 80 ohms and you're using 50 ohm coax, the best SWR you can achieve is 1.6 to 1.
SWR really messes with the ham mind, especially with beam antennas where the SWR curve is hardly ever centered on the resonant frequency of the antenna because the feedpoint impedance at resonance is rarely 50 ohms. The SWR curve is therefore skewed to one side or the other of resonance and non-symmetrical. The worse the mismatch of the coax and the antenna at resonance, the greater the skewing effect and asymmetry of the
SWR curve.
Note: Visit http://www.k5ua.com for details of his 40 meter two element phased array.
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Links to other Ham Radio related papers authored by KG9OM
- Click other photos for additional Amateur radio photographs of interest.
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Being a good "Elmer" (Amateur Radio mentor) involves much more than assisting someone to pass the license examination. I've always been eager to do my part to welcome new operators to the HF bands. Most new hams develop their operating practices--most good, but some not so good--simply by listening to more-experienced hams. I like to urge them to learn Good Operating Practices . << Click this link to read my suggested guidelines based on what I've learned from listening to other hams since 1972. My philosophy is that amateurs who develop good operating practices will help sustain Amateur Radio's "long and proud tradition of self-regulation."
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Click >> Electric Radio... Alive and well to view a PowerPoint presentation KG9OM provided to the Murray State University Amateur Radio club 02/03/04. This presentation examines why and how to restore vintage ham radio equipment.
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Click >> Enhanced SSB Audioto view a PowerPoint presentation KG9OM provided to the Murray State University Amateur Radio club 10/07/03.
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Click >> Boat Anchor Radio Restoration Project which showcases KG9OM's restoration of a vintage Johnson Viking Valiant 10-160 meter AM/CW transmitter, Hammarlund SP-600 receiver and Heathkit Marauder transmitter.
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Microphone reviews:
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