Re: LF: To DK7FC : measuring low levels RF current.

["Alan Melia" <alan.melia@btinternet.com>]



Stefan try a look at http://g4hup.com/RFC/RFC.htm

its 100ma/1A full-scale. Follow the documentation, click under the pic and find the circuit and cal procedure which should give a clue to reading higher currents too.

 

Alan

G3NYK 

----- Original Message -----

From: DK7FC

To: rsgb_lf_group@blacksheep.org

Sent: Friday, October 23, 2015 11:03 PM

Subject: Re: LF: To DK7FC : measuring low levels RF current.

Hello Andi,

Thanks for the info. What does this amperemeter cost?
I think i would know how to build an amperemeter for 100 mA FS. However my ranges are 5A / 10A / 20A :-) I'm directly measuring the antenna current, i.e. not on the 50 Ohm level.

73, Stefan

Am 23.10.2015 14:53, schrieb F6CNI - Andy - JN19QB:

Helo Stefan,

 

For info, here I am using a MFJ 834 RF Ammeter. It is working well on MF band, it just need to be first re-calibrate on MF band (only one variable resistance to adjust) using a low power signal into a 50 Ohms pure resistive load.

 

It is quite linear for RF current measurement from 25 mA to 3 Amperes, in 3 swiched scales.

 

Using it on the 50 Ohms coaxial cable, just after your TX output, you have a good estimation of your TX power output from 30 milli watt to 450 watts.

 

You can also use it on the cold end of the antenna side. Depending at the overall antenna system resistance, you can read the real antenna current…

 

73 de Andy.

 

From: DK7FC

Sent: Thursday, October 22, 2015 11:09 PM

To: rsgb_lf_group@blacksheep.org

Subject: LF: M0LMH

 

Hi MF,

Since a few hours i'm transmitting WSPR with the variable mains transformer turned to 0%. So just the driver is switching the FETs. Anyway a few mW TX power seem to be generated and radiated. I can see no reading on the RF amperemeter.
Anyway i got 15 spots:

Timestamp	Call	MHz	SNR	Drift	Grid	Pwr	Reporter	RGrid	km	az
2015-10-22 20:14	DK7FC	0.475685	-22	0	JN49ik	1	M0LMH	IO93gx	862	310
2015-10-22 20:24	DK7FC	0.475683	-19	0	JN49ik	1	F5WK	JN18hp	452	261
2015-10-22 20:44	DK7FC	0.475682	-21	0	JN49ik	1	PA0A	JO33de	449	339
2015-10-22 20:14	DK7FC	0.475682	-26	0	JN49ik	1	PA0RDT	JO11tm	428	305
2015-10-22 20:14	DK7FC	0.475683	-17	0	JN49ik	1	PA3ABK	JO21it	386	315
2015-10-22 20:14	DK7FC	0.475683	-15	0	JN49ik	1	DH5RAE	JN68qv	345	98
2015-10-22 20:14	DK7FC	0.475683	-18	0	JN49ik	1	PI4THT	JO32kf	336	338
2015-10-22 20:14	DK7FC	0.475683	-15	0	JN49ik	1	DJ0ABR	JN68nt	329	101
2015-10-22 20:14	DK7FC	0.475683	-22	0	JN49ik	1	DG8RW	JN69cv	257	77
2015-10-22 20:14	DK7FC	0.475682	-23	0	JN49ik	1	DF2JP	JO31hh	256	325
2015-10-22 20:54	DK7FC	0.475683	-27	1	JN49ik	1	DC0DX_H	JO31lk	255	332
2015-10-22 20:24	DK7FC	0.475684	-24	0	JN49ik	1	DB1EPO	JO31hg	252	325
2015-10-22 20:14	DK7FC	0.475684	-21	0	JN49ik	1	DF6NM	JN59nj	175	91
2015-10-22 20:14	DK7FC	0.475684	-7	0	JN49ik	1	DK2DB	JN48fw	58	198
2015-10-22 20:34	DK7FC	0.475686	-10	0	JN49ik	1	DF8UO	JN48ex	56	206

M0LMH is the best distance. Also in daytime i can see that M0LMH is receiving me, often beeing the only one from UK.
Does someone know him and his equipment? Would be interesting to know! In IO93GX, there is not population. Certainly one reason for the good results...

73, Stefan

PS: Now QRO...