Bird Elements

[ZL1SWW]

Hi All,
Some time back, I picked up a Bird element 500 C1 - 100 - 250 MHz 500 Watt slug. Now it reads high compared with my other slug and also my 4304 meter. I am trying this in my Bird 43 meter. Now a normal slug is just called 500C and this original one from bird is labelled "500 C1". Anyone know what this one is meant for? I suspect it is for another meter movement other than the standard 30 uA. I think there are some meters that are 100 uA. No hits on google and nothing on the Bird site that I can see.

Any clues??

Also posted this on the VK/ZL VHF-UHF Facebook page.

Cheers.

Simon
ZL1SWW

[VK6ZFG]

Hi Simon

The element is listed by Bird as:

Product Description: C1 Series, 100-250 MHz Standard Elements, 100µA on http://www.btgstore.com/10mhzplelc1s.html
Now while the more common inserts are for 30uA it may be possible to re calibrate the 100uA one you have to work with a 30uA meter.

Inserts have an internal pot for calibration purposes. This is under the disc on the front of the insert. This disk can be removed by placing this end of the insert in a shallow bath of petrol to loosen the adhesive used to fix the disk to the insert body. I did this to one that was out of calibration. I fixed the disk back on using PVA Wood Glue (I will need to use water to remove the disk next time).

You will need to check the readings at a few meter deflection positions to make sure the readings are tracking correctly. Now if the pot adjustment does not provide the desired results the next (and better) option is to add a resistor inside the insert in parallel with the meter contacts. This would be so that with full scale deflection, the meter takes 30uA and the resistor 70uA. You will need to determine what value resistor you need to use.

The white cap on the insert is held in place by a screw under the disk.

Hope this helps

Igor
VK6ZFG