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Reviews For: MFJ 1048

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Review Summary For : MFJ 1048
Reviews: 3MSRP: 139
Description:
Passive Preselector
Product is in production
More Info: http://www.mfjenterprises.com/Product.php?productid=MFJ-1048
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0033.3
N2EIK Rating: 2020-12-04
Good but needs a slight addition. Time Owned: more than 12 months.
I have some out of band interference on 80 meter that sporadically wipes me out. It made net participation frustrating. I purchased this unit as a desperate attempt to help. It worked and worked well. I really dont have any other issues on other bands to make any remarks so for my issue on 80mtr its a "two thumbs up".
The only thing it really (really!) needs is some sort of indicator light, so that I know its on. If I forget it activated and change bands, I am wondering for a few moments why my incoming signal is practically nil. Hmmm, maybe that speaks volumes about "out of band rejection"?
K1ZH Rating: 2019-06-14
Works as advertized Time Owned: more than 12 months.
First of all, you need to remember that most ham radio manufacturers design their transmitters with a target of -30dBc for higher-order IMD products. Now if you add a little phase noise to that mix of interference-causing RF energy, what you get is a hash of interference across the spectrum. If you've got a neighbor operating a ham transmitter QRO, a portion of his RF-hash will land smack-dab in the middle of your SWL-band. The MFJ-1048 is essentially a simple BP-filter and it is not designed to reject noise from the pass-band; it can only reject out-of-band interference.

So the solution to problems like KM5VI describes is to install a high power BP-filter on the local transmitters so that the RF interference is not TRANSMITTED to nearby stations. Blocking transmitter noise is orders of magnitude simpler than attempting to remove interference at the receiver.

Anyway, the purpose of the MFJ-1048 is to remove interference from out-of-band sources. Such as, from a local broadcast-band transmitter that is overloading the front-end of your receiver.

I tried one of these and it performs as advertised. Therefore, I'm giving it a good rating.
KM5VI Rating: 2009-05-12
Poor Performance Time Owned: more than 12 months.
This product did not meet my expectations. I purchased the unit to improve the rejection of strong out of band signals, in particular, another ham operating QRO in my neighborhood during contest season. I did not find that the unit could make any meaningful improvement. The unit would, in fact sometimes false trigger the pin diode keying relay just from strong received signals without transmitting from my station, requiring me to externally key the unit (there is a jack provided). Save your $$$.