I have this coming into the workshop over the next day or so, does anyone have a schematic for this tuner. The fault description I have is that it will no longer tune on at least one band, specifically 7mhz. I will post pictures in due course of disassembly once I have the tuner on the bench.
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Re: MFJ 994BRT (remote Antenna tuner)
Haven't come across "a one band not working" on big automatic antenna tuners like that. I am guessing a cold solder joint on an inductor, bad relay or a smoked HV tuning capacitor in the tuning section.Last edited by CapLeaker; 05-08-2019, 06:14 AM. -
Re: MFJ 994BRT (remote Antenna tuner)
schematic for itComment
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Re: MFJ 994BRT (remote Antenna tuner)
Yeah that is what I am thinking, thanks for the schematic. The guy still has to remove the tuner from a 30 foot pole that its installed on. Been rather windy these last few days, will put up an update when I get the unit in the workshop.Comment
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Re: MFJ 994BRT (remote Antenna tuner)
Well finally got the tuner, nothing much to see with this one, couple of relays tested bad. Replacements ordered and fitted, the real test will be when the unit is back in service since although it tests out good on the antenna system I have here I doubt the system has the same tuning profile and or characteristics that the clients install has.Last edited by llonen; 05-16-2019, 07:45 PM.Comment
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Re: MFJ 994BRT (remote Antenna tuner)
usually they are easy to repair if the damage is in the tuning section. There isn't much there and that's a good thing.Comment
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Re: MFJ 994BRT (remote Antenna tuner)
i thought antenna tuners went on the desk next to the radio???Comment
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Re: MFJ 994BRT (remote Antenna tuner)
not these ones. They go outside and are automatic tuning. Look at this MFJ or SGC-230. These are more efficient, since you are tune there where it matters, at the antenna. Think of it as an electronic self adjusting tuning box or balun. The only downside is, you need another cable (power) to it.Comment
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Re: MFJ 994BRT (remote Antenna tuner)
This one has the option of sending the supply through the coaxial cable, the most efficient place for an antenna tuner is at the feed point of the antenna since it avoids all the losses from the reflected RF back down the cable which ends up as losses to heat. The downside is the cheaper ones have no easy management, if you need to work on them IE make adjustments to how they tune or carry out a reset you need to access the internal controller. That said the 600 watt and upwards tuners are not cheap, and they don't really tune at 600 watts. Tuning has to be carried out at low power before ramping up the RF.Comment
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Re: MFJ 994BRT (remote Antenna tuner)
I had forgotten about sending the power in the coax feature. On the SGC-230 etc you need to put a separate power and control cable.Comment
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Recently I switched from my Gray-Hoverman to the Antennas Direct ClearStream 4 MAX. Seems to work about as well as the old G-H in my attic (one-story ranch home), but the Antennas Direct unit can be mounted outside on my chimney if desired.
I should mention that I was also using a 29-inch "T" shaped antenna for RF channel 11. I know you're not supposed to use TWO antennas unless they have the same length coaxial cable going into your combiner (and even then there might be problems). So I made sure the cables were equal length.
Years ago I made a "T"... -
Hello all, I've been looking into this portable air conditioner's remote control and can't find what could be causing the problem - or possibly this remote is just terribly designed.
The remote only works at exactly 3V - if I drop it any lower, using my bench power supply, to say, 2.9V then the remote will not flash the display and turn off. I don't have any AAA batteries that are exactly 1.5V each so I'm not sure if this remote is designed this way - to only use the freshest possible batteries, or if there's a failed component in the mix.
I can't find any schematics... -
TAOGLAS ANTENNA MODEL: ISPC.86A.09.0092E
The specs says ...
High antenna efficiency 868MHz ISM Band
5dBi Peak (when placed on 30cm x30cm ground plane) - Broadside to Zenith Radiation Pattern
The antenna is 50x50 mm square and How do I fix it on the Ground Plane of 300 x 300 mm (aluminium sheet 3mm thick).
1. Should I Fix it with a glue.
2. Should I fix it with a double side adhesive tape
3. Should I fix it with Screws (the screw head may just clamp the antenna to the aluminium...12-09-2024, 11:06 AM -
All,
I recently moved to a very rural area. I am about 25 miles from the nearest urban settings (2 separate College Towns). 45-50 miles from a Urban City (Toledo Ohio)
There was a Omni-directional Wineguard Antenna (amplified) that was mounted on the house originally. Came with the house. Center of the top of Roof a few feet from Chimney on a 4 foot pole. The 75 ohm line went from the roof down 2-3 stories to the small Wineguard amplifier and then it split to the living room and master bedroom. Currently a Very simple setup.
Since we moved in, 8 years ago,... -
Hello everyone,
I was wondering if anyone could help my in pairing a remote with a Toshiba fire tv?
The Tv model number is: 50lf711u20 Rev B.
I've already replaced all the the circuit boards within the tv along with the I.R. sensor receiver.
I've tried 3 different remotes which should be fully compatible with this TV.
Oddly enough. A few if the buttons on all of the remotes actually work. Even without pairing...which makes no sense.
The power button, along with the volume,back,select, and directional...
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