Although it is a Ham Band antenna for 40,20,10....you might try listening to General Coverage and tune to 10, 15 or 20 MHz for WWV......see if you can hear it.....from what you say, I doubt it, and if so, you have a radio set up issue, IMHO.....Rick
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Sun, Jan 31, 2021 at 8:45 PM Rick Hiller <[email protected]> wrote: > Mark, A few questions, comments and tests: > Sounds like a radio problem to me...so....not in any particular > order, just what I thought of first to last.... > . > -- What S level is the noise? Does it change level with the RF Gain > control? > -- What if you disconnect your antenna coax? Does it go away? > -- What if you connect a dummy load? Same noise? > -- What does the Nano VNA show? Impedance wise (R and j) and SWR? What > is the SWR bandwidth of the antenna across 40 and 20? > -- Where is your RF Gain pot? Maxed? Try reducing the setting a bit. > -- Do you have your "pre-amp" on? If so, turn it off. NB off too. > -- What about CW mode....does the Narrow filter on make a difference? > -- Where are the IF/PBT shift sliders set? They should be in the center > for a base reference. > > -- Are the rear panel Receive Antenna In and Out jacks jumpered and is the > jumper OK continuity wise? > > -- Is the Ham/General select switch in Ham position? I am not sure if the > band pass filters are bypassed in General....just a guess. > > -- Take your coax off. Then using ONLY the center pin of the PL-259 > insert it into the radio SO-239 center ONLY. Is the noise similar? Then > screw on the PL-259 outside....does the noise change? Usually, using only > the center pin causes lots of receive noise and then when you screw on the > 259 outside the noise reduces as the antenna system is then a closed system. > You can also do this with a 10 foot long piece of wire and just connect > the wire to the inside center terminal of the SO-239 on the radio. The > receive noise should increase when you touch the wire to the center > pin......is this noise the same as you are complaining about? > > Have you run power to the antenna? What is the SWR? Similar to the Nano > reading? Use the internal SWR meter and meter switch to select RF PWR and > SWR set etc. > > That's about it for a 745 brain dump for tonight. Something is amiss in > your set up, IMHO, no external wideband white noise source is jacking with > ya. Sounds like receiver noise is at max gain and no received signals are > being processed. > > GL and 73...rick -- W5RH > > > > > > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> > Virus-free. > www.avast.com > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> > <#m_8022499859921838938_m_5532074014698849640_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > On Sun, Jan 31, 2021 at 7:33 PM Mark Brantana via BVARC <[email protected]> > wrote: > >> I am reaching out for ideas on a radio issue. I have installed an IC-745 >> Icom with an MFJ-2010 offset fed dipole. The power supply is a 20A MegaWatt >> switching power supply, which is located right next to the radio. The >> antenna is under some high power-lines with the long leg 90 degrees to the >> power-lines. I used my nanoVNA to study the band SWR response, and >> everything looks reasonable, though some small adjustments may need to be >> made. Nothing is grounded as yet. >> >> Here’s my problem. I am only attempting to receive at this time and I get >> consistent QRM white noise across all bands to the point where I can barely >> pick out some voices, etc. >> >> >> - I am confident that the antenna is properly connected due to my >> antenna study. >> - I don’t believe the power lines are an issue, since the problem >> would likely be more isolated show up as birdies at certain frequencies. >> - The radio settings seem to all be correct according to the manual. >> >> >> - Lack of grounding, but again the white noise is generally >> consistant across the spectrum. Still, this could be the problem. >> - I have turned off my computer, so there no QRM from its power >> supply. >> - It does not help to have the switching power supply right next to >> the radio, but other users give good reports on this model and no QRM >> issues are mentioned. >> - I tried the radio at different times of the day on 20-m voice band, >> with the same noisy result. >> - It could be the net result of a large number of small device >> transformers, but I doubt it. >> - I turned off the wifi, and still no change. >> >> >> Hmm… I am a little stumped. Any thoughts or ideas? Personal experiences? >> >> Mark >> N5PRD >> ________________________________________________ >> Brazos Valley Amateur Radio Club >> >> BVARC mailing list >> [email protected] >> http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org >> > > > -- > Rick Hiller > *e-mail: [email protected] <[email protected]>* > *Cell: 832-474-3713* > *Physical: 9031 Troulon Drive* > * Houston, TX 77036* > > > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> > Virus-free. > www.avast.com > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> > <#m_8022499859921838938_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > -- Rick Hiller *e-mail: [email protected] <[email protected]>* *Cell: 832-474-3713* *Physical: 9031 Troulon Drive* * Houston, TX 77036*
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