Sony STRDH590 antenna

So this was a full duplex link ?

What was the frequency separation between Tx and Rx ?

On the satellite, what was the physical R/Tx separation at the antenna(s) ? I guess it is much smaller than the separation between ground based Tx/Rx antennas.

When you have to use the same antenna for both Rx and Tx, you of course need a notch filter against the Tx frequency inserted in front of the Rx chain. In most cases, you also need a notch tuned at the Rx frequency inserted into the _Tx_ chain to reduce the Tx phase noise falling on the Rx frequency. A larger Rx/Tx frequency separation also helps.

This is most easily seen with third order input intercept point (IIP3) measurements. The 2f1 - f2 intermodulation product is nasty, since it can fall directly on a weak signal you want to measure. If the offending signals f1 and f2 are a few MHz away from the desired Rx frequency, a tuned section in front of the mixer will take care of them, but if the offending signals are within 1 MHz from the desired signal, both can pass the RF filter generating intermodulation products which fall on the IF frequency and thus also pass the IF filter. Thus the IIP3 figures with a small separation of offending is much worse compared to greater separation.

that used all PNP RF transistors in the signal path. That isn't a problem other than having to buy the 1000 at a time. Luckily, that company went ban krupt. I serviced hundreds of designs and all used AGC for RF and IF.

from the ground, until it was in space, where there wasn't enough land to p rovide decent physical seperation.

No, it wasn't. It was for Telemetry, not communications. Communications was provided by other equipment that was built in Europe.

Sigh. My high school's Amateur Radio club built a two meter repeater in the late '60s. That included the required filters. I was a Broadcast engine er where we combined Aural and Visual transmitters to a single antenna. Hav e you ever worked with one that would handle 200KW at the old Analog Ch55?

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excessive RF, and producing Intermod.

There were sites where a tunable trap with steep skirts was needed to at tenuate an unwanted signal. That included schools when their local Cable TV company decided to scramble Ch3 with a strong CW signal in the guard band. Available MATV amps al overloaded, and wiped out the channels used for Edu cational TV. I designed and built a seven stage trap that didn't cause ripp le in the level across the available channels.

I had no access to a spectrum analyzer so they were aligned with a signal g enerator and a 1n*@ UHF mixer diode as a detector. I also had to use a pair of 50 to 72 ohm transformers for impedance matching. The resulting notch w as clean enough for them to feed the Ch 3 modulator into the system, and el iminate the switching between CATV and local. Physical components didn't ex ist for a 75 Ohm trap, so it was transformed to were it could be built. us ed glass piston trimmers, and a heavy, diecast Pomona box. Sheet bras was u sed to divide the interior into compartments, and to improve the isolation between filters. The seams were all soldered, including the covers.

So what was your problem ?

It sounds that you had a bad gain and selectivity distribution in the Rx chain ?

Using a two meter repeater with a common Rx/Tx antenna and 600 kHz separation through a duplexer is standard practice, three cavities in the Tx chain and three cavities in the Rx chain is enough.

Things got complicated due to multiple FM BC transmitters feeding a common FM BC antenna a few meter from our 2 m repeater antenna. Most problems were due to intermodulation products due to rusty bolts in the nearby structures. Removing those obsolete structures helped a lot for a few years. Unfortunately two FM BC stations were assigned frequencies 600 kHz from each other, Unfortunately the third order mixing product of those two FN BC signals and repeater Tx frequency fell directly on the repeater Rx frequency, making the repeater receiver more or less useless.

Rusty bolts will produce a lot of intermodulation products on sum and difference frequencies :-).

te from the ground, until it was in space, where there wasn't enough land t o provide decent physical separation.

ns was provided by other equipment that was built in Europe.

Sigh. Being under a half mile from the launch site drove the LNA into sa turation.

The receivers were tripe conversion, and had a LINEAR 0 to +5 AGC system allow an accurate Diversity system that could track to under 1/10dB, and t he output level was adjustable over a 63dB range in 1/10dB steps. You can't seem to wrap your mind around the fact that agencies were lined up to buy these at around $20,000 each. They filed two rack spaces per Receiver or Co mbiner. NOAA, NASA and the ESA bought them, and one receiver was built to o perate off 48VDC for the ISS.

in the late '60s. That included the required filters.

ters to a single antenna. Have you ever worked with one that would handle 2

Of course. Even rusty barbed wire has crude semiconductors at their join ts. Rusty tower bolts can also weaken to the point that they fracture and a re ejected from a tower leg.

The tower at that TV station had two UHF TV stations, Eight, 50 KW FM trans mitters. A trunking radio system with a large room crammed full of Motorola base stations, and a cluster of Government repeaters. The only named agenc y was the U.S. Forestry service. There was plenty of isolation on that 1700 ' tower. The lowest antenna was the FM antenna for the FM stations. It was at 1000 feet above ground.

Cracked waveguide with 185KW of RF can cause nasty burns, too. One tower worked received a long, narrow burn on his ass from just bumping int the c orner of that several ton piece of brass.

Hummmm.... a trip down memory lane. Sounds like an Alan-Dick antenna.

It was the big stick in Orange City, Florida :)

It is a 2 position Molex but the is only one I could see on the receptacle. There is only one pin in the plug; the one with the wire attached.

Only 1.