RF Limiters

[N9JIG]

Having popped a few multicouplers over the years as well as deafening a couple scanners I figure it is about time I invest in some RF Limiters for protection. Better late than never!

I am considering the Stridsberg LIM-01WB as it has BNC's on it so I would not need adapters. At $130 each (I need 4) that is gonna be a bit pricy however.

Anyone have any other suggestions?

 

[sallen07]

I am considering the Stridsberg LIM-01WB as it has BNC's on it so I would not need adapters. At $130 each (I need 4) that is gonna be a bit pricy however.

That's what I ended up getting. I have one in my shack that I added in front of my multicoupler when I put up an EFHW HF antenna with the balun box on the same TV antenna mount where my scanner antenna lives, and I put one in my truck "just in case" since I'm running a 2m/70cm mobile as well as a scanner.

 

[kruser]

I've used these LIMITER / SMA / RoHS | VLM-33W-2W-S+ | Mini-Circuits in the past.
Not sure how effective they are compared to the Stridsberg model but they are about half the cost of the Stridsberg.
Mini-Circuits does not appear to have a BNC version though.

 

[sonm10]

Look on eBay for Hewlett Packard limiters
This is the closest link I could find

Hewlett Packard 5086-7284 Limiter

Hewlett Packard 5086-7284 Limiter Microwave Components Coaxial Microwave Coaxial Microwaves

bmisurplus.com

 

[N9JIG]

Look on eBay for Hewlett Packard limiters
This is the closest link I could find

Hewlett Packard 5086-7284 Limiter

Hewlett Packard 5086-7284 Limiter Microwave Components Coaxial Microwave Coaxial Microwaves

bmisurplus.com

I looked at these before and would need a couple adapters to make them work, I am hoping to find a decent value with BNC's so I can keep the insertion loss down.

 

[vagrant]

I use those HP limiters. I believe I purchased them for $20-$25 each via eBay. The slight loss at home is resolved with a 10dB amplifier, which also makes up feed line loss, filters, etc. and gives me a little gain in the end. In the vehicle no amplifier, but the TX antennas are much closer. The limiter keeps things friendly.

Perhaps purchase one Stridsberg and one of the HP with some adapters. Then check your numbers using an analyzer and then later each inline with an SDR to compare and contrast again with your system. You could probably sell one of them on RR later, or use it in your vehicle.

 

[Ubbe]

Most limiters have the same +10dBm limit and 10nS switch time, equal to the conducting voltage of two standard diodes in parallel but in different directions and their switch time. Limiters usually also have a max input level that equals a standard 1 Ampere diodes max current.

/Ubbe

 

[prcguy]

I’ve purchased many HP/Agilent 10w limiters similar to this one off eBay real cheap. they are very good for protecting VHF/UHF receive systems and have very little insertion loss.

HP / Agilent 5086-7261 0 to 2.5 GHz, 10 W, SMA (F-F) RF Coaxial Limiter | eBay

(HP / Agilent. and rice-paper to protect lenses, mirrors and other optical parts. available). wire transfer. requested otherwise. best solution for you if possible.

www.ebay.com

 

[N9JIG]

I just ordered 3 of the Stridsberg LIM-01WB (Bias-Tee) RF Limiters, as well as a batch of double-female BNC adapters. I will report the status once they arrive.

I plan on using 2 on the car, one for each of the 536's. I think I might have to use short jumpers as space is limited behind the radios and the devices might not fit attached directly to the radio. The third will go on the multicoupler used for the scanners in my rack in the office.

 

[N9JIG]

So here is a question: Are RF Limiters polarized? Does it really matter which direction they are placed in line?

I looked at the HP 5086 series and some have SMA females at both ends, such as the 5086-7261 mentioned above. This would require a double male at the radio side.

The 5086-7284 has a female at one end and male at the other. Unfortunately it shows "Input" on the female side and "output" on the male side. Assuming the input side is for the antenna this would be backwards and require adapters at either end. If not, then this could be placed in line with no adapters. Is this assumption correct or not?

My friend is considering these and would like to save some money but until we know whether the scanner will be protected if we connect it "backwards" we are hesitant.

I received my Stridsberg LIM-01WB's yesterday and they seem to pass RF in either direction. I did need a double male BNC to connect to the multicoupler and in the car will require that or a short jumper (depending on the room available behind the scanner when I dig into it). If anyone is interested, here is a picture of the interior of the device:



The main component is a MIni-Circuits RLM-33-2W, I assume the 2 small black devices are resistors and the smaller white devices are voltage regulators.

 

[prcguy]

The 1002 device is a 10k ohm resistor across the input and output and the small white squares are capacitors in series with the RF in and out paths. The large white device is the limiter, which will only handle up to about 2w and will pass up to 5dBm before limiting starts.