Jump to content
  • 0

Antenna issue (suspected)- receive is excellent, transmission is lacking.


dwmitchell61

Question

I have a 40W Midland MXT-400. A 1 foot jumper of TM LMR-400 connects the output to an MFJ-842 SWR/POWER meter rated 140MHz-500MHz. A 3 foot RG-8X jumper connected to my window feed through (MFJ-4601N, N connectors). On the outside I have a lightning protector (also N connectors). The feed line is 30 feet of TM LM-400 connecting a BRC HP500 antenna.

The SWR meter indicates 35W output from the radio with approximately 2W reflected power and the needles cross at 1.4SWR.

A call to an individual I hear booming in from a repeater loud and clear with only two bars on my signal meter tells me that my signal is staticky and broken. So it appears that the receive is a LOT better than my transmission.

I suspect that I have an antenna marketed as a GMRS antenna that is in fact a UHF antenna trimmed for SWR, but not necessarily a GMRS resonant antenna. The ad says it is 3 5/8-wave on 2m and 7 5/8-wave on 70cm, and the frequency is 460-470MHz (GMRS) and "C-loaded" (ceramic capacitor at the bottom, probably?).

Any thoughts on this?

Thank you,

Dave KJ7WUZ/WRHW845

Link to comment
Share on other sites

13 answers to this question

Recommended Posts

  • 0

Just a thought:

Are you sure you have the radio set for repeater split operation, or are you possibly transmitting on the repeater's output freq? (and not + 5MHz)    Than might explain the strong signal you are receiving (from the repeater) and the weak signal that the other station is reporting (since they are hearing you 'direct' and not through the repeater.)

Link to comment
Share on other sites

  • 0
42 minutes ago, dwmitchell61 said:

I have a 40W Midland MXT-400. A 1 foot jumper of TM LMR-400 connects the output to an MFJ-842 SWR/POWER meter rated 140MHz-500MHz. A 3 foot RG-8X jumper connected to my window feed through (MFJ-4601N, N connectors). On the outside I have a lightning protector (also N connectors). The feed line is 30 feet of TM LM-400 connecting a BRC HP500 antenna.

The SWR meter indicates 35W output from the radio with approximately 2W reflected power and the needles cross at 1.4SWR.

A call to an individual I hear booming in from a repeater loud and clear with only two bars on my signal meter tells me that my signal is staticky and broken. So it appears that the receive is a LOT better than my transmission.

I suspect that I have an antenna marketed as a GMRS antenna that is in fact a UHF antenna trimmed for SWR, but not necessarily a GMRS resonant antenna. The ad says it is 3 5/8-wave on 2m and 7 5/8-wave on 70cm, and the frequency is 460-470MHz (GMRS) and "C-loaded" (ceramic capacitor at the bottom, probably?).

Any thoughts on this?

Thank you,

Dave KJ7WUZ/WRHW845

What is the antenna?  If it is a dual band that includes 2m, it is not likely to be resonant on 64cm (GMRS), especially repeater input.  Being seven 5/8λ stacked for UHF it'll have an even tighter operational bandwidth, but will give much higher gain.  The SWR reading from the meter might not be accurate.

Link to comment
Share on other sites

  • 0
Posted (edited)

Yes. The settings are correct. I double checked. I use the programming software. That way I can use the slots for the normally unused channels 8-14 to put in more repeaters and set it all for wideband operation (among other things). It makes it a lot easier than using the front panel, also.

I replaced a broken Comet CA-712EFC with this one. The performance for a 17 foot antenna compared to the 712 at 10 ft 4 in is abysmal. Internally the BRC HP-500 seems to be just wire antenna elements. The Comet CA-712EFC was a coaxial collinear internally with coaxial stub matching transformers at the base.

Edited by dwmitchell61
Added more details of antennas
Link to comment
Share on other sites

  • 0

The SWR meter could be off, it IS an MFJ product.  The BRC HP-500 antenna was advertised as a GMRS antenna. The "Frequency:" range was given as the GMRS, but they also mentioned the "Gain:" as being so much at "2m" and "70cm".

I suggest buying the Comet CA-712EFC antenna before I would buy the BRC HP-500, for GNRS, anyway. 

Link to comment
Share on other sites

  • 0

Almost no antennas truly transmit on the one (and only one)  frequency where they are resonant, yet they transmit well enough. 
Although that’s an MFJ SWR meter and the numeric value might be incorrect, it still will show you where the SWR is the lowest, so I wouldn’t worry too much about that. 
Like WSAM454, I absolutely would suspect that the frequency you are transmitting is the 462.xxx MHz frequency instead of the 467.xxx MHz frequency. I’m sure you set it right in software, but radios sometimes try to outthink us. Try using one of the factory repeater channels (23-30) with the correct CTCSS or DCS tone. 

Link to comment
Share on other sites

  • 0

Yeah, I know. Analyzers can get expensive. Slowly building my shack on a tight budget. I might look into a VNA, but you have to watch what brand if those you are buying, also. The Chinese aren't known for their quality checks, that's for sure. 

Link to comment
Share on other sites

  • 0

The Comet CA-500 is a good and simple antenna analyzer to use. Yes they do cost more but are worth it. Above that you are looking at the Rig Expert analyzers. I normally steer clear of most MFJ products.

The different VNA and Nana VNA models are cheaper but there is also a learning curve to using them.

Link to comment
Share on other sites

  • 0
13 minutes ago, dwmitchell61 said:

Yeah, I know. Analyzers can get expensive. Slowly building my shack on a tight budget. I might look into a VNA, but you have to watch what brand if those you are buying, also. The Chinese aren't known for their quality checks, that's for sure. 

I bought the NanoVnA from R and L electronics. It is well built and has N connectors rather than SMA. Used with nano Vna saver software it’s a piece of cake to use. But it’s not my favorite. 

I’ve worked on an MFJ 269D analyzer. They’re poorly built and I would never buy one. 


Now I have two different RigExpert analyzers. I really like them. They are my favorites. 

Link to comment
Share on other sites

  • 0
1 hour ago, Sshannon said:

I’ve worked on an MFJ 269D analyzer. They’re poorly built and I would never buy one. 


Now I have two different RigExpert analyzers. I really like them. They are my favorites. 

I sent my MFJ 269D and 849 back to MFJ last September under warranty because of erroneous readings. They were never consistent readings. They were suppose to recalibrate the meters.

I received my 269D towards the of February. I still don't have the 849 and I don't care if I ever get back the 849. I even gave up on the 269D about mid January and receiving the 269D was a total surprise. The 269D still gives inaccurate readings.

I am happy with my RigExpert 650 although the battery charger for the rechargeable  batteries they sent is a POS and won't fully charge the batteries. I rectified that problem by buying a charger from Walmart for about $50.

I'm about to throw out the 269D and if anyone wants it at no cost, all you have to do is pre-pay the shipping cost and provide a shipping label and it's yours. But I wouldn't trust the readings with it.

Link to comment
Share on other sites

  • 0
2 hours ago, nokones said:

I'm about to throw out the 269D and if anyone wants it at no cost, all you have to do is pre-pay the shipping cost and provide a shipping label and it's yours. But I wouldn't trust the readings with it.

I’m tempted. I’m actually in Phoenix right now. Maybe I could give it to my friend. He’s a ham and would enjoy having anything. 

Link to comment
Share on other sites

  • 0

A friend con me in going to the HAM thing at DeVry University with him this Saturday and if you or your friend is going to this HAM thing I can bring the 269D with me and give to you or him.

Let me know if that will work.

Link to comment
Share on other sites

  • 0
3 hours ago, nokones said:

A friend con me in going to the HAM thing at DeVry University with him this Saturday and if you or your friend is going to this HAM thing I can bring the 269D with me and give to you or him.

Let me know if that will work.

I’ll probably be playing with the grandkids on Saturday but I appreciate your offer. My friend is back in Montana. 
I actually feel a little guilty even asking for it. There may be others who need it more than my friend.

Take it to the ham thing and trade it or sell it!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Guidelines.