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Old 04-06-2011, 15:02   #91
olegsher
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Really good point!!
But this was done on purpose - the SATCOM system is asymmetrical - the Satellite Vehicle Platforms (Satellites) are more powerful (150W) than ground stations (5-20-50W). Additionally, SWR is much more important on the transmit side - we can pull out the signal lost on the receive side with som LNA (Low Noise Amplifier), but you cannot do anything with the transmit power lost due to the impedance mismatch.
Ground Stations Rx frequencies are 240-270Mhz, Tx Frequencies 270-320Mhz.
The optimization on SWR was favoring Tx portion of the band with the ratio of 4:1 over the SWR on Rx side.
Quite opposite was done for the Gain - the geometry was optimized to get the maximum gain on Rx portion of the SATCOM band.
The final optimization was to find the best balance between those two contradicting requirements.
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A Couple of points
Old 04-06-2011, 20:09   #92
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A Couple of points

Quote:
Originally Posted by olegsher View Post
Really good point!!
But this was done on purpose - the SATCOM system is asymmetrical - the Satellite Vehicle Platforms (Satellites) are more powerful (150W) than ground stations (5-20-50W). Additionally, SWR is much more important on the transmit side - we can pull out the signal lost on the receive side with som LNA (Low Noise Amplifier), but you cannot do anything with the transmit power lost due to the impedance mismatch.
Ground Stations Rx frequencies are 240-270Mhz, Tx Frequencies 270-320Mhz.
The optimization on SWR was favoring Tx portion of the band with the ratio of 4:1 over the SWR on Rx side.
Quite opposite was done for the Gain - the geometry was optimized to get the maximum gain on Rx portion of the SATCOM band.
The final optimization was to find the best balance between those two contradicting requirements.
I read your response with some interest and I will offer you a few things to consider.

When I said you had a “significant variance” well, that was an understatement. Because of the sensitivity of TACSAT receivers TACSAT antennas designs try to stay below 2:1. The entire premise that you optimize the uplink band is incorrect, as you are only comparing power transmitted without considering the receiver portion of the link. Unlike the ground terminals, the satellite has an array of high efficiency antennas, sensitive receivers and a clean electromagnetic environment. The ground terminals, on the other hand, have a lower sensitivity and are very susceptible to harmful interference from other emitters. They are further handicapped by scintillation effects as well as ground effects (diffraction, super and sub refraction, etc…) in certain environments. LNA’s will often exacerbate the noise issue, as they themselves may only generate a small amount of noise, but they will happily amplify any environmental noise or other interference in the receive path. All of these effects degrade the receive sensitivity and require more signal in order to achieve link—something the satellite cannot compensate for. They also have to accommodate the loss of power from the satellite transponders as they age.

You stated that you optimized the gain of the RX side (and I still would like to see your plots), but your model significantly degrades the efficiency of the downlink band from barely acceptable at 259 MHz to atrocious at 240 MHz via the SWR indicated. I was also troubled by your plots, as they indicate gain at zenith (dBic) to be 6.3 and your 3dB beamwidth to be ~110 degrees. Assuming an Omni-directional radiation pattern your gain at peak of beam should be closer to 0dBic. Either you have an error in your chart, or the model does not exhibit a 360 degree radiation pattern.

The antenna in this thread has been around for a while and is generally accepted to work. I recommend you review your model more before you make further suggestions to change it. A couple of links that provide background:

Combating Low UHF-SATOM Downlink Margin—a White paper prepared by Raytheon E-Systems
http://www.argreenhouse.com/society/...pers/38-03.pdf

MIL-STD-188-181A Interoperability Standard for Single Access 5 KHz and 25 KHz UHF SATCOM Channels (also available on AKO)
http://rodolfo.ips.es/HTML/06radio/S...S/m188181a.pdf

Interference on UHF SATCOM Channels, Barrie Strachan, SPAWAR, San Diego
http://www.argreenhouse.com/society/...ers99/36_6.pdf

Multi-Service Tactics, Techniques and Procedures for UHF TACSAT and DAMA Operations, FM 6-02.9 (available on AKO)
http://www.uhf-satcom.com/uhf/r3403g.pdf
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Again, good points!!
Old 04-06-2011, 21:30   #93
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Again, good points!!

Thank you for keeping good and interesting discussion.
I have all documents that you mentioned, except SPAWAR one, in my library, but SPAWAR is a real good read - thanks again.
My argument will be - if you look at the distribution of the Rx frequencies on majority of the 25KHz channels, all of them start at 252MHz and up. The 244-252 MHz band is used for narrowband 5KHz channels, and usually they are allocated for ANDVT traffic. In all our requests for SATCOM we were always given 25KHz channels, both for DAMA and dedicated. That's why I decided to assign a lesser weight to that 244-252 Mhz band.
Second, the SWR is much more critical to Tx side - in HF radios (PRC-138, PRC-150 ALE for example), the SWR minimization tuning is only done on Tx, but not Rx side. And there is a valid reson for that - if you have bad SWR on transmit, then in all radios ALC (Automatic Level Control) kicks in when the SWR is usually more than 1:1.5, and as the result, the output power is immediately reduced, hitting you with the double wammy. That also prevents the output cascades of the power amp from frying when your antenna is not connected or is short circuited (SWR is really bad then). On the other hand, the receive side SWR is not that important. Basically it boils down to "You can receive with any piece of wire, but you cannot transmit into any piece of wire".
And that brings us to your good point about directivity (beamforming) of the antenna. This is what important on receiving, when it is necessary to properly filter useful signal from the environmental noise (as the article you suggested points). And for this antenna by its design, without additional reflectors (like in AV 2055-3) there is no way to get any serious suppression of the sidelobes.

Again, the point of computer simulation and optimization was to create an antenna that will behave nicely in a wide frequency range, without the need to recalculate and retune.
To convert the dimensions that I provided to the L = 1005/F formula, the equivalent sizes are: FTX = 318MHz, FRX = 251MHz, so this is not a big change from the original design. The most important thing that I would like to stress is the addition of the polarizer - the 8" wire that gives you extra 3dB of gain for RHCP relative to a isotropic antenna.

Last edited by olegsher; 04-07-2011 at 00:46.
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Forgot to answer one question
Old 04-06-2011, 21:55   #94
olegsher
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Forgot to answer one question

I forgot to answer the question on the gain.
Usually you can either normalize the gain, or have it graphed relative to isotropic radiator. I used the later.
Just for comparison - here are calculations for the Avant-Trivec 2055-3, and as you can see the results are pretty dead on what they claim:
Frequency 240-318MHz
VSWR 1.5:1
Polarization Right Hand Circular
Gain +10.5 dBi, 244-318 MHz
Power Handling 200 Watts CW
Axial Ratio 3 dB at half power points
Weight 3.1 pounds
Connector BNC Female

You can see that the attached charts give the same result.
Attached Images
File Type: jpg Ant_AV2055-3-1.jpg (41.2 KB, 117 views)
File Type: jpg Ant_AV2055-3-3.jpg (92.0 KB, 90 views)
File Type: jpg Ant_AV2055-3-2.jpg (61.7 KB, 77 views)
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Using the R-amp with MBITR
Old 04-07-2011, 11:38   #95
allester666
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Using the R-amp with MBITR

I would just like to add some notes to this discussion. The expedient SATCOM antenna has worked for my element with great success. I would like to point out to anyone using this design using a R-AMP from TSE something stated in the manual...The R-AMP is a low noise amplifier. This is a feature that doesn't match up perfectly when using an MBITR for VX SATCOM through the SATCOM port. Hook up your radio/antenna to the LOS adapter on the R-AMP to get the best results, which I have had great ones using an MBITR through a R-AMP. Best of luck, and thank you for this discussion
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Old 04-07-2011, 12:47   #96
69harley
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To clarify, the RAMP-25 provides 10db of gain on it's dedicated SATCOM port. The amplifier is also able to operate on SATCOM frequencies while in the LOS mode. The LOS port operates on the entire 30-512 MHz range but does not provide any receive amplification. The RAMP-25 provides 18-40 watts Rf output depending on input DC voltage and RF input.

The commo gods at TSE Inc have recently come out with their new MB50 amplifier. I saw Ed get 50 watts out of the MB50 while connected to a single BA-5590. The new amp has a better form factor, increased power output, added waveforms and improved output connectors. The LOS connector is now the same as the big radios, which allows us to connect the same whip and donkey dick antennas we use not he big radios.
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File Type: pdf Amp MB50 11.2.15.pdf (464.3 KB, 69 views)
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Filter Tune PSC 5
Old 04-29-2011, 12:12   #97
Electron
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Filter Tune PSC 5

Try filter tuning your PSC-5 with the antenna. This might help with a BIT fault you might get. See thread link below.

http://www.professionalsoldiers.com/...ken+Soup+PSC-5
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Old 01-08-2012, 11:28   #98
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FYI, I did some checking into the Tricom/TSE amplifier debate and Tricom originally designed and made the RAMP-25, RAMP-75 and several other amplifiers where TSE was a reseller of these items but apparently got a trademark on the "RAMP-XYZ" name.

TSE and Tricom eventually had a falling out and TSE had another company design and manufacture a look alike amp to the Tricom units which is what they now market.

The Tricom made RAMP-25 was JTIC certified in late '07 and the Tricom made RAMP-75 was certified in late '06, both were sold through TSE and other vendors.

The newer TSE RAMP-25 and 75 designed and made by a third party for TSE came out in early '09 and were later certified.

Bottom line is, Tricom is not a fly by night company, they are the originators of this series of amps and TSE was a reseller of their products.

I'm not trying to trash TSE in any way, just pointing out some facts.

Respectfully,
Radio Guy




Quote:
Originally Posted by 69harley View Post
The JITC website tells no lies. According to JITC, TSE Inc certified the RAMP-25 and RAMP-75 several years before Tricom came out with what looks like a knockoff of the TSE products.

I have personally used several of the knock off units made by Tricom and everyone of them failed miserably. Even had the engineer/designer/owner of Tricom slam his amp on the bench to get it to work.

The guys at TSE Inc are from this community and build great stuff. Just makes sense that some fly-by-night company would copy them.
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Old 01-09-2012, 07:29   #99
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That does not make sense. JITC is where MANUFACTURERS have their products certified. Funny that not a single other 'reseller' had an amplifier certified. EVERYONE with equipment listed on the JITC website is a manufacturer. Tricom didn't come on the scene until several years after TSE. Looks like Tricom copied a product designed, manufactured and cretified by the good people at TSE, most of which happen to be Quite Proffessionals. Your information is skewed.
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Old 01-09-2012, 09:08   #100
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I own two RAMP-75 and two AM-SAT-50 amps and have first hand knowledge of the two companies, no skewed info here.

I purchased the two TSE labeled RAMP-75 amplifiers from an asset recovery company (lost UPS shipment stuff) and they appeared NIB but had problems. I contacted Ed at TSE who was very gracious in getting me info and suggestions on troubleshooting the units but in the end they were well beyond user repair.

Ed at TSE finally put me in contact with the designer and manufacturer of these amplifiers which was Tricom Research, I still have the emails from Ed on this.

Tricom is not far from my location and after some conversations Tricom agreed to waive the usual checkout fee for an out of warranty unit and I was at their front door at 8am the next morning with one of the amps.

I toured the Tricom factory, met some of the design, assembly and test team and I can tell you with my past career at Hughes Aircraft designing and building microwave and RF equipment I can say the operation is first class.

Tricom found my units had been shipped to an end user, were defective and were lost in the return mail back to TSE or the factory. The guys at Tricom proceeded to replace a defective board supplied by another vendor while I waited. They ran it through final QC and handed me the repaired amp and a printout of its performance at no cost. Tricom later repaired the second defective unit at no charge to me. How is that for service?

Ed at TSE did his best to help but in the end the unit was out of warranty with his company and TSE did not appear to have on site manufacturing or repair capabilities to handle a repair like this.

I also inquired about the Tricom/TSE connection and received info and timelines of who designed what and who sold what for who. These amps have model #s assigned by Tricom but TSE trademarked the "RAMP" designation for these products which they sold. If you look at any of the amps made before around 2009 they can have the TSE RAMP sticker and the original Tricom part # on the same unit.

A Google search also find the info on lawsuits between the two companies, and timelines where you can see Tricom made and supplied these amps and other equipment to TSE and other resellers.

With Google searches you will also find its very clear that after the Tricom/TSE split, TSE had a third party company design and manufacture a new line of amplifiers with similar looks and footprint to the Tricom products and TSE continues to sell them under the "RAMP" trademark. The new line of TSE amps had to be re-certified after their release in early '09 even though they have the same or similar part #.

Just trying to clear up some misinformation that was posted here, my dealings with TSE are very positive and Ed is a very knowledgeable and experienced commo guy. I will speculate on some of the confusion with JITC certification which could be from TSE owning the "RAMP" trademark and the early Tricom amps were submitted under the RAMP designation. Maybe Ed can chime in on this.

On the other hand Tricom is not a fly by night copy cat company, they are the real deal in amplifier design and manufacturing. I regularly use my RAMP-75 amp with a neutered MBITR and other handlelds in support of USCG comms and in testing of prototype antenna products.

Radio Guy



Quote:
Originally Posted by 69harley View Post
That does not make sense. JITC is where MANUFACTURERS have their products certified. Funny that not a single other 'reseller' had an amplifier certified. EVERYONE with equipment listed on the JITC website is a manufacturer. Tricom didn't come on the scene until several years after TSE. Looks like Tricom copied a product designed, manufactured and cretified by the good people at TSE, most of which happen to be Quite Proffessionals. Your information is skewed.
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Hey Y'all
Old 01-07-2018, 09:56   #101
rubberducky
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Hey Y'all

So I tested this in country and I made a few tweaks to it. But seriously great job and thanks for posting this. I used WD-1 and it made the rating a bit better as well as a few expedient cobra heads. I have it strapped to my flak for a better constant asset. Thanks again guys if you want ill post a picture of how I built it. Also I built a few with some pop cans. By the way, standard 550 cord is great not only as an insulator but to put whatever cabling you have inside of it to protect it a little more. Thanks again,

Rubberducky
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Old 01-20-2018, 08:39   #102
rwt_bkk
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always good to have an update with pics if you have them...
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